27 Types of Drafting

Various types of drafting have wide applications that are highly relevant to the goals of each specialized drafting field or discipline. The most common types of drafting are as follows:

1. Airplane/aircraft drafting

Airplane drafting is the type of drafting for aircraft structures, including helicopters, airplanes, rockets and spaceships and their components.

2. Architectural drafting

Architectural drafting is drafting done for architectural and structural features of houses and buildings based on building codes/specifications, building materials (steel, reinforced concrete, timber, masonry, etc.), and construction methods.

3. Automotive drafting

Automotive design drafting is the type of drafting carried out for automotive vehicle components, assemblies, systems, and various kinds of motor vehicles that have four wheels and are propelled by an internal combustion engine or power that creates propulsion or different movements via its own force or momentum.

4. CAD/AutoCAD drafting

CAD/AutoCAD drafting is drafting that is done for every imaginable type of engineering, architectural, and technical projects, and includes the use of specifications, notes, codes, and dimensions in accordance with industry standards.

5. Cartographic drafting

Cartographic drafting is drafting performed for maps, spatial data in graphic or digital form, and other purposes including but may not be limited to: social, legal, design, political, and educational purposes, respectively. Cartographic drafting may require geographic information system (GIS) for capturing, storing, analyzing, manipulating, managing, and demonstrating all types of natural and built features, political boundaries, and geographic or spatial data.

6. Civil drafting

Civil drafting is drafting conducted for civil engineering projects such as houses, installations, sewage disposal systems, water systems, bridges, roads, highways, dikes, culverts, wharfs, pipelines, breakwaters, flood-control projects, etc.

7. Commercial drafting

Commercial drafting involves the preparation of drawings concerning layouts that may include but not be limited to: plans for arrangement of offices and also for store buildings, large rooms, factories, and drawing charts, forms, and records. Commercial drafting can also be applied to engineering drawings and designs or 3-D rendered models for manufacturing and production, documentation packages, specifications, material lists, and commercial contracts which can be analyzed to detect the most significant concerns.

8. Design drafting

Design drafting is the type of drafting in which various kinds of software applications are used to create technical drafts of engineers’ and architects’ designs and drawings and develop CAD models that can facilitate the production of prototypes, final designs, and manufacturing.

9. Electrical drafting

Electrical drafting is drafting performed for cable installation and cable layout, circuit-board assembly diagrams, industrial establishments, general wiring diagrams, power plants, electrical distribution systems of domestic and commercial buildings, layout drawings of electrical equipment, and wiring in communication centers.

10. Electronic drafting

Electronic drafting is the type of drafting conducted for the assembly, installation and repair of electronic devices, electronic components, printed circuit boards, and equipment. Electronic drafting also involves the use of electronic schematics and related documents to develop, compute, and verify specifications in drafting information, such as tolerances, configuration of parts, and dimensions.

11. Furniture drafting

Furniture drafting is drafting done for different models of countless types of furniture and walk-in wardrobes, including their design.

12. Geological drafting

Geological drafting is the type of drafting for cross-sections, maps, profiles, well logs, topographical surveys, subsurface formations, geophysical formations, geologic formations, and directional surveys to represent geophysical or geologic stratigraphy and locations of oil and gas deposits.

13. Geophysical drafting

Geophysical drafting is conducted for rock formations by using data obtained from geophysical prospecting activities and involves preparing diagrams and maps based on computations from gravity meters, petroleum-prospecting instruments, recordings of seismographs, magnetometers, and surveying field notes.

14. HVAC (heating, ventilating, and air-conditioning) drafting

HVAC drafting is performed on heating, ventilation, and air-conditioning systems and components, including refrigeration equipment, chilled water schematic layout and fresh air/exhaust air schematics, building ductwork and related structures required in different types of building design plans suitable for the space assigned within a house or building structure.

15. Industrial Process-Pipe drafting

Industrial process-pipe drafting is the type of drafting carried out for oil and gas industrial pipe arrangement layouts and its construction methods, and procedures or processes in refineries, oil and gas fields, process-piping systems, chemical plants, gasoline plants, steel frames, pipeline systems/piping manifolds, drilling derricks, compressor stations, etc.

16. Interior design drafting

Interior design or interior drafting is conducted to create representations of the interior parts of structures and showcase the placements of electrical and plumbing appliances, floor coverings layouts, existing wall layout, furniture layout, ceiling plan, electricity plan, plumbing plan, and wall elevations along with their respective cross sections.

17. Landscape drafting

Landscape drafting is the type of drafting made for garden structures along with the grading, drainage, lighting, paving, planting, and irrigation of the gardens, and general landscaping as well.

18. Mechanical or Machine drafting

Mechanical drafting or machine drafting is the type of drafting conducted on all kinds of machinery used in the vast engineering drafting industry, including fastening and joining tools or equipment, machinery and mechanical devices.

19. Marine drafting

Marine drafting is performed for the structural and mechanical features of all kinds of marine or nautical equipment and structures, including ships, shipboard, ship decks, submarines, boats, and docks.

20. Patent drafting

Patent drafting employed in drafting certain documents for patent lawyers to use in obtaining patent rights or sole rights to an invention.

21. Plumbing drafting

Plumbing drafting shows the system of piping for water that is going into buildings and wastewater that is being discharged from buildings; generally speaking, it may show gas, plumbing, and piping equipment and installations in different types of residential, commercial, and industrial buildings or settings.

22. Sheet-metal drafting

Sheet-metal drafting is for drafting of sheet metals or metal sheets that are slight or lacking in thickness, such as thin sheets which are usually represented by thin lines and an included surface.

23. Ship or Naval drafting

A ship or naval drafting is the type of drafting specifically on ships, shipboard, and ship decks, including the transverse and longitudinal profiles and cross sections of ships and any equipment that has widely used in ships or ship building projects.

24. Structural drafting

Structural drafting is done for structures or structural components such as, but may not be limited to: wood, concrete, steel reinforcement, reinforced concrete, masonry, etc. Structural drafting includes drafting of installations, plans, details of foundations, floor and roof framing, building frames, etc.

25. Technical illustration drafting

Technical illustration drafting is done to communicate messages, stories, or ideas in books, greeting cards, advertisements, magazines, and newspapers. It includes using illustration software and different kinds of colors and effects to prepare technical manuals and brochures for assembling, installing, operating, maintaining, and repairing machines, equipment, and tools.

26. Tool-and-Die Design drafting

Tool-and-die design drafting is the type of drafting conducted for mechanical designs and product development of tool and die manufacturing and automation and metal stamping tool and die design in accordance with specifications and designs indicated by standard tool designers.

27. Topographical drafting

Topographical drafting is performed to draft elevations, traverses, and topographical maps from aerial photographs and surveying notes, modify topographical maps, and make maps (i.e., map drafting) or plots for various purposes.

30 Types of Drafters

Drafting is as extensive as some other non-drafting fields. It is so broad that there are several types of drafting or related drafting occupations for different types of drafters within each drafting field.

Different types of drafters perform duties that are relevant to the goals of their respective specialized drafting fields or disciplines. The most common types of drafters are as follows:

1. Aeronautical/airplane drafter

An aeronautical or airplane drafter is the type of drafter who creates drawings and/or computer-aided drafting/design (CADD) models of:

• airplanes and their components.
• spacecraft and their components.
• rockets/jet engines and their components.
• ballistic missiles or projectiles  and their components.
• general launch mechanisms.
• other aero-related machines and their components.

2. Architectural drafter

An architectural drafter prepares drawings and/or CADD models of countless types of architectural and structural features of houses and buildings by referring to or relying on knowledge of building codes/specifications, building materials (steel, reinforced concrete, timber, masonry, etc.), and construction methods.

3. Automotive Design drafter

Automotive design drafter creates drawings and/or CADD models of automotive vehicle components, assemblies, systems, and various kinds of motor vehicles that have four wheels and are propelled by an internal combustion engine or power that creates propulsion or different movements via its own force or momentum.

4. CAD/AutoCAD drafter

CAD/AutoCAD drafter is the type of drafter who:

• creates drawings and/or CADD models of the final versions of construction projects, including specifications, notes, codes, dimensions, materials and methods of production.
• uses CAD and SolidWorks software to prepare accurate technical drawings that are up to industry standards.
• converts designs into drawings, schematics, plans and other related documents; in addition, a CAD drafter updates existing drawings while making use of the software’s library of standard drawing templates.

5. Cartographic drafter

Cartographic drafters gather geographic information from geodetic surveys, satellites, and aerial photos, and analyse and interpret the same. In addition, they conduct research, acquire valuable information, and use it to prepare maps and other spatial data in graphic or digital form for different purposes which may include but not be limited to: social, legal, design, political, and educational purposes, respectively. 

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A cartographic drafter or cartographer can also be able to develop geographic information system (GIS) for capturing, storing, analyzing, manipulating, managing, and demonstrating all types of natural and built features, political boundaries, and geographic or spatial data.

6. Casting, Forging, and Mold Drafter

Casting, forging, and mold drafters prepare detail drawings and 3D models—including geometric dimensioning and tolerancing (GD&T) specifications—that are used in designing supports for molds and dies and creating essential models for producing computer numerical control (CNC) machine files along with every bit of vital information required in machining processes.

7. Civil drafter

A civil drafter is the type of drafter who creates detailed drawings and/or CADD models of big, small, and all kinds of civil engineering projects such as houses, installations, sewage disposal systems, water systems, bridges, roads, highways, dikes, culverts, wharfs, pipelines, breakwaters, flood-control projects, etc. Furthermore, civil drafters use drawings to estimate the volume of fill material or excavations required in earthmoving operations.

8. Commercial drafter

Commercial drafters are also known as facilities drafters. They prepare drawings or CAD models for layouts that may include but not be limited to: plans for arrangement of offices and also for store buildings, large rooms, factories, and drawing charts, forms, and records. A commercial drafter produces engineering drawings and designs or 3-D rendered models for manufacturing and production, documentation packages, specifications, material lists, and also washes and paints colored drawings when required.

9. Design drafter

A design drafter is the type of drafter who:

• uses various software applications to create technical drafts of engineers’ and architects’ designs.
• analyzes blueprints and schematics and works with manufacturing engineers to create engineering drawings and develop CAD models that can facilitate the production of prototypes, final designs, and manufacturing.

10. Directional survey drafter

Direction survey drafters:

• make estimations and prepare drawings that represent certain characteristics such as direction of inclination, degree, depth, diameter, location of equipment, and other dimensions and characteristics.
• use photographic subsurface survey recordings and related data to create drawings and/or computer-aided drafting/designs of oil-well boreholes or gas-well boreholes.

11. Electrical drafter

Electrical drafters prepare diagrams for cable installation and cable layout, and produce drawings and CADD models of circuit-board assembly diagrams, industrial establishments, general wiring diagrams, power plants, electrical distribution systems of domestic and commercial buildings, layout drawings of electrical equipment, and wiring in communications centers.

12. Electronic drafter

Electronic drafter is the type of drafter who produces drawings and CADD models for the assembling, installation, and repair of electronic devices, electronic components, printed circuit boards, and equipment. Electronic drafters assess electronic schematics and related documents that help in developing, computing, and verifying specifications in drafting information, such as tolerances, configuration of parts, and dimensions.

13. Furniture drafter

Furniture drafters create casework drafting and millwork drafting (both are drafts/blueprints of real-life wooden furniture) and drawings and/or CADD models of different types of furniture and walk-in wardrobes, including their design, with the goal of maximizing space. These aspects of drafting are important to the work of furniture manufacturers and interior designers.

14. Geological drafter

Geological drafter is the type of drafter who prepares diagrams, cross-sections, maps, profiles, subsurface formations, and directional surveys to represent geophysical or geologic stratigraphy and locations of oil and gas deposits. Geological drafters also correlate and interpret data acquired by conducting topographical surveys, from well logs, and from geophysical prospecting reports. In addition, geological drafters use special symbols to represent oil field installations, geophysical formations, and geologic formations.

15. Geophysical drafter

Geophysical drafters create drawings and/or CADD models of subsurface contours in rock formations by using data obtained from geophysical prospecting activities; geophysical drafters prepare diagrams and maps based on computations from gravity meters, petroleum-prospecting instruments, recordings of seismographs, magnetometers, and surveying field notes. A geophysical drafter is sometimes referred to as seismograph drafter, depending on the prospecting method or activity they engage in.

16. HVAC (heating, ventilating, and air-conditioning) drafter

HVAC drafters:

• prepare drawings of sized and routed systems to conform to the space assigned within a house or building structure.
• draw plans for installing refrigeration equipment and prepare chilled water schematic layout and fresh air/exhaust air schematics.
• develop 3-D models and detailed HVAC shop and installation drawings.
• draft MEP (mechanical, electrical and plumbing) coordination layout.
• prepare external and internal site coordination drawings, plant room coordination drawings, and building ductwork drawings.

17. Industrial Process-Pipe drafter

Industrial process-pipe drafters are sometimes referred to as “industrial pipe drafters”, “pipeline drafters”, or “piping drafters”. Even an “oil and gas drafter” who specializes in oil and gas industrial pipe drafting is sometimes referred to as an industrial process-pipe drafter.

Industrial process-pipe drafters prepare maps that represent geologic stratigraphy and create drawings and/or CADD models for layouts, construction, and procedures or processes in refineries, oil and gas fields, process-piping systems, and chemical plants.

Industrial process-pipe drafters also prepare detailed drawings for constructing gasoline plants, steel frames, pipeline systems and piping manifolds, drilling derricks, compressor stations, masonry buildings; furthermore, they also prepare drawings for fabricating, manufacturing, and assembling machine parts and machines.

18. Interior drafter

Interior drafters prepare drafts or detailed interior drawings and CADD models for 2-D graphic representations of interior parts of structures, as they apply to general construction or renovation purposes.

Interior drafters create drawings that showcase the placements of electrical and plumbing appliances, floor coverings layouts, existing wall layout, furniture layout, ceiling plan, electricity plan, plumbing plan, and wall elevations along with their respective cross sections.

19. Landscape drafter

A landscape drafter is the type of drafter who creates drawings and/or CADD models from rough sketches or information acquired from landscaping and conducting site surveys, grading and drainage assessments, lighting designs, paving designs, planting designs, irrigation designs, and from drawings that include details of garden structures.

20. Mechanical or Machine drafter

Mechanical drafters or machine drafters create drawings and/or CADD models of countless kinds of machinery used in the vast engineering drafting industry, including fastening and joining tools or equipment, machinery and mechanical devices; in addition, they prepare multiview drawings of parts required in manufacturing and repairing machines and equipment.

21. Marine drafter

Marine drafter is the type of drafter who creates drawings and/or CADD models structural and mechanical features of all kinds of marine or nautical equipment and structures, including ships, shipboard, ship decks, submarines, boats, and docks. Marine drafters consider the appropriate assembling and fastening methods and refer to specifications used in the manufacture of all types of marine and naval vessels.

22. Patent drafter

Patent drafters prepare patent drawings or accurate drawings of mechanical devices used on certain documents by patent lawyers to obtain patent rights or sole rights to an invention.

23. Photogrammetry drafter

Photogrammetry drafters prepare original maps, contour-map profile sheets, mosaic prints, aerial photographs (including topography, contour points, hydrography, and cultural features), charts, planimetric or topographic features, and every type of cartographic-related material that requires mastery of photogrammetric techniques and principles. Photogrammetry drafters also prepare 3-D relief models of plastic, rubber, or plaster.

24. Plumbing drafter

A plumbing drafter, also known as a pipe drafter, creates drawings and CADD models for installation of plumbing and piping equipment in different types of residential, commercial, and industrial buildings or settings: the drawings could be for fixtures and pipes needed to distribute water or gas in buildings and sewage tanks or systems for disposing wastewater from buildings.

25. Sheet-metal drafter

Sheet-metal drafters develop drafts for sheet metal by using design principles or CADD software package; generally, they apply the principles, rules, and conventions of mechanical drawing to produce drawings of objects that are slight or lacking in thickness, such as thin sheets which are usually represented by thin lines and an included surface.

26. Ship or Naval drafter

A ship or naval drafter is actually a marine drafter who specializes in ship drafting which is not as broad in scope as marine drafting. Ship drafters develop drawings and/or CADD models of the structural and mechanical features in ships, shipboard, ship decks, including the transverse and longitudinal profiles and cross sections of ships, any equipment that has wide application in ships or ship building projects.

27. Structural drafter

Structural drafters create drawings and/or CADD models for structures or structural components such as, but may not be limited to: wood, concrete, steel reinforcement, reinforced concrete, masonry, etc. Structural drafters also create installation drawings and drawings of plans and details of foundations, floor and roof framing, building frames, and other structures.

28. Technical illustration drafter

Technical illustration drafters combine hand-drawing and painting skills to produce still drawings and images that help to communicate messages, stories, or ideas in books, greeting cards, advertisements, magazines, and newspapers.

Technical illustration drafters refine or make improvements on designs by using illustration software and employing different kinds of colors and effects to prepare technical manuals and brochures for assembling, installing, operating, maintaining, and repairing of machines, equipment, and tools.

Also, technical illustration drafters prepare drawings from blueprints, models, and photographs techniques appropriate for final usage or specified reproduction processes.

29. Tool-and-Die Design drafter

Tool-and-die design drafter is the type of drafter who prepares drafts useful in mechanical design, product development, tool and die manufacturing and automation, metal stamping tool and die design, SolidWorks 3D modelling; in addition, tool-and-die design drafters create detailed drawings and/or CADD models of manufacturing tools in accordance with specifications and designs indicated by standard tool designers.

30. Topographical drafter

A topographical drafter is a civil drafter who specializes in plotting elevations, laying out traverses, drafting topographical maps from aerial photographs and surveying notes, modifying topographical maps, and making maps (i.e., map drafting) or plots for various purposes.

Who is a Drafter in Engineering and Architecture?

The drafting aspect of engineering, architecture, and technology is crucial in contemporary times and to the future of every country. Thus, technical drafting or drawing is a fundamental part of every engineering and architectural drafter’s education, with much emphasis on precision manufacturing and interchangeability in contemporary times which requires that drafters be educated enough to properly interpret instructions provided on drawings, and help engineers and architects construct or build objects and structures.

The term drafter in the fields of engineering and architecture (and other fields where it is applicable) refers to anyone who has been educated and trained in visualizing, creating, and interpreting technical drawings for objects, structures, products, and many applications, especially in regard to how they are designed to function. Drafters specialize in the drafting profession which employs standard methods to represent objects, structures, designs, specifications, and ideas in a consistent manner.

A drafter is familiar with materials, drawing tools/equipment, and methods used to construct drawings that define exactly what needs to be constructed, built, produced, or manufactured. In many cases (probably more often than not), drafters assist engineers in the design process to create technical drawings for documenting designs and producing or manufacturing products.

Drafters produce technical drawings and plans used in engineering and architecture by production, manufacturing, and construction workers to build countless kinds of objects and structures.

An architect or engineer (and even surveyors, architects, or scientists) may task a drafter with filling in technical details using drawings, specifications, rough sketches, and calculations that have been made. For example, architects or engineers may ask drafters to use their knowledge of projection and drawing techniques to draw the details of a structure they have imagined and sketched on paper.

Some drafters are educated enough to use their knowledge of technical drawing and manufacturing theory and standards to determine design elements, determine the types and numbers of fasteners required to assemble different machines, and draw different parts of machines. Drafters can use tables, technical handbooks, calculators, and computers to prepare technical drawings and assist in various kinds of design.

Some drafters are often called CADD operators (i.e., computer-aided design/drafting operators) because they are educated and trained in creating and storing drawings, electronically, on computer.

Other titles that can be used in place of drafter include but may not be limited to:

• draftsperson
• design drafter
• drafting technician
• engineering drafter (civil, mechanical, electrical, aeronautical, etc.)
• architectural drafter
• CADD drafter
• CADD operator
• CADD technician

The job title of a drafter could also be discipline-specific or task-specific; for instance, a drafter who works for or is attached to a civil engineer is called a civil engineering drafter, a construction drafter, a civil drafter, or civil CADD technician. The term civil cuts across because it refers to the design, construction, and maintenance of physical and naturally built objects or structures in the environment or society environment, which included houses, bridges, roads, sewage systems, canals, dams, etc.

Types of Parallel and Perspective Projection

In order to produce different types of technical and engineering drawings in today’s world, one would have to make projections by projecting lines of sight on different planes of projection, at least mentally or in the imagination—even if not on paper. It’s possible to apply lines of sight on an object with or without the physical presence of that object.

A plane of projection is a two-dimensional plane on which the shape of an object or structure is projected. The two-dimensional plane is only imaginary—i.e., it exists mainly in the imagination to help capture the shape or image of objects or structures from different directions of lines of sight.

One common misconception floating around is that projection and drawing always mean the same thing, even when in many cases they don’t, especially to people who use different types of projections as a means of creating different types of technical and engineering drawings.

Projections are usually done mentally, and may be drawn on paper or illustrated in books for the purpose of teaching. Projections are not necessarily the same as technical and engineering drawings; they are only the means to an end, which is the different types of technical and engineering drawings.

Two main types of projection used to create different types of technical and engineering drawings: parallel projection and perspective projection. These two main types of projection consist of different categories or types which will be defined a bit later in the post:

• Types of parallel projection: orthographic projection and oblique projection. Orthographic projection can be expressed via multi-view projection or axonometric projection.
• Types of perspective projection: aerial perspective projection and linear perspective projection.

Figure 1: 2 Types of parallel projection and 2 types of perspective projection (brown rectangles). Orthographic projection can be further expressed through multiview projection and axonometric projection (gray rectangles)

Parallel projection can be used to create nine types of technical or engineering drawing through its types (orthographic and oblique projections) or subtypes (multiview projection and axonometric projection): first-angle, second-angle, third-angle, fourth-angle, isometric, dimetric, trimetric, cavalier, and cabinet drawing, respectively.

13 Types of Engineering Drawing (Free PDF Download Available)

On the other hand, perspective projection can be used to create four other different types of technical or engineering drawing via its types (aerial perspective projection and linear perspective projection): aerial, one-point, two-point, and three-point drawing, respectively.

Figure 2: 13 types of drawing (yellow rectangles) created from different types of parallel and perspective projection

Types of parallel projection

Parallel projection is the type of projection in which projectors, also called “lines of sight” or “imaginary lines”, are projected from a position (the eye of a viewer or anywhere) in such a way that they are parallel to each other and at the same time perpendicular to the planes of the object(s) they are projected upon. The plane of the object is also the plane of projection.

In parallel projection and the different types of parallel projection, the lines of sight are parallel to each other and do not converge at any point, as is the case with perspective projection where the lines or sight converge at or emerge from one or more points, depending on the type of drawing that has to be produced.

Figure 3: The difference between the line of sight in parallel projection and the line of sight in perspective projection

There are two types of parallel projection: orthographic projection and oblique projection. Orthographic projection can be expressed either as multiview projection (which displays as many important views as necessary) and axonometric projection (which can display a single important view in 3-D):

1. Orthographic projection

Orthographic projection is the type of parallel projection in which parallel projectors are projected in a perpendicular direction on the major planes of a 3-D object and the corresponding 2-D representations of the object are drawn on media such as paper and computer screen. 

Figure 4: Orthographic projection of an object (Image credits: Google.com and Dreamcivil.com.)

As stated earlier, orthographic projection can be expressed either as multiview projection or as axonometric projection.

(A) Multiview projection

Multi-view projection is the type of orthographic projection or subtype of parallel projection in which parallel projectors are perpendicular to the major planes or essential parts of an object such as the top, front, and side views (possibly including other important sides) of an object which are all represented individually in 2-D on paper or computer.

Multi-view projection is actually a projection of many orthographic projections or views all in one place or on media such as paper or computer screen. Multiview projection is employed in creating first-angle drawing, second-angle drawing, third-angle drawing, and fourth-angle drawing.

Figure 5: Quadrants used in multi-view projection to create first-angle, second-angle, third-angle, and fourth-angle drawings, respectively (Image credit: Google.com.)

Figure 6: Third-angle drawing (3 major views) produced via multiview projection

Figure 7: Six principal views of a 3-D object created by multi-view projection

The 6 Principal Views of 3D Objects from Multiview Projection

15 Examples of the 6 Principal Views of Objects/Structures

(B) Axonometric projection

Axonometric projection is the type of orthographic projection or subtype of parallel projection in which parallel projectors are perpendicular to a chosen direction and planes of a 3-D object that is tipped or rotated about one or more of its major axes (x, y, and z) to reveal various sides (top, side, and front views), with the projection expressed on a drawing as a single view that has some foreshortened dimensions.

Axonometric projection is used in creating three different types of technical or engineering drawing: isometric drawing, dimetric drawing, and trimetric drawing.

Figure 8: Axonometric projection of an 3-D object (Image credit: Peachpit.com.)

2. Oblique projection

Oblique projection is the type of parallel projection in which the parallel projectors are parallel to each other but not perpendicular to any planes of the 3-D object they are projected on and one of the three planes of the object is projected at either 30°, 45°, or 60° to the x-axis. Angle 45° is used in most oblique projections.

Since the parallel projectors are not directly perpendicular to any of the 3-D object’s plane, it results in technical or engineering drawings that have true shapes and sizes on only one or two planes/faces. Oblique projection is used in creating two types of technical or engineering drawing: cavalier drawing and cabinet drawing.

Figure 9: Oblique projection of objects (Image credit: Slideplayer.com.)

Types of perspective projection

Perspective projection is the type of projection in which the projectors or lines of sight originate from the same point (called point of convergence or vanishing point) and diverge away from each other the more they approach an object’s plane of projection, thereby resulting in drawings of objects that appear smaller the more their distance increases away from the vanishing point, eyes of the observer, or eyes of the projector.

Figure 10: The difference in orientation between the projector in parallel projection and the projector in perspective projection

Perspective projection is sometimes called perspective view or perspective drawing or simply perspective: the lines of sight in perspective projection start at a single point and move towards an object, or converge at a single point away from an object.

Figure 11: Perspective projection: center of projection (viewpoint, vanishing point, convergence point, or eye of observer) (Image credits: Art-Design-Glossary and Google.com.)

The main difference between parallel projection and perspective projection is that while the lines of sight remain parallel to each other and do not converge at some point in parallel projection, the lines of sight do converge in perspective projection. 

There are two types of perspective projection: aerial perspective projection and linear perspective projection.

1. Aerial perspective projection (also known as atmospheric perspective)

Aerial perspective projection is the type of perspective projection in which the projectors diverge away from their point of convergence (or vanishing point) unto the planes of projection, and color, tones, and atmospheric effects or features are used to produce a 3-D aerial drawing of the shape of the object—a shape that would appear smaller the more the object’s distance increases away from the observer or vanishing point.

The use of color and tones usually creates the illusion of depth on a 2-D surface such as paper or computer screen. Aerial perspective projection is used in producing aerial drawing which is one many types of technical or engineering drawing.

Figure 12: Aerial perspective projection of a concrete building (Image credits: GenesisStudios and YouTube.)

2. Linear perspective projection (also known as geometric perspective)

Linear perspective projection is the type of perspective projection in which a set of construction rules are employed in such a way that the projectors or imaginary lines of projection diverge away from their point of convergence (or vanishing point) unto the planes of projection, and a 3-D drawing outlining the shape of the object is produced without necessarily having to add the kind of color, tones, and atmospheric effects or features that usually indicate the effect or atmosphere on the appearance of an object.

Linear perspective projection is used in creating three types of technical or engineering drawing: one-point drawing, two-point drawing, and three-point drawing.

Figure 13: Linear perspective projection of some boxes (Image credits: Dreamstime.com and Pinterest.com.)

20 Multiview Projection Examples (Front, Top, and Side Views)

The following 20 multiview projection examples show how the three principal views of different types of 3-D objects or structures are represented on technical, engineering, and architectural drawings, respectively:

1. Multiview projection example of an object (front, top, and side views)

Figure 1

2. Multiview projection example of part of the steps of a staircase in third-angle drawing (American system)

Figure 2

3. Multiview projection example of an in first-angle drawing (European system)

Figure 3

4. Multiview projection example of a concrete structure in third-angle drawing

Figure 4

5. Multiview projection example in third-angle drawing

Figure 5

6. Multiview projection example in third-angle drawing

Figure 6

7. Multiview projection example in third-angle drawing

Figure 7

8. Multiview projection example in third-angle drawing

Figure 8

9. Multiview projection example in third-angle drawing

Figure 9

The Planes of Projection in Multiview Projection

The 6 Principal Views of 3D Objects from Multiview Projection

15 Examples of the 6 Principal Views of Objects/Structures

10. Multiview projection example in third-angle drawing

Figure 10

11. Multiview projection example in third-angle drawing

Figure 11

12. Multiview projection example in third-angle drawing

Figure 12

13. Multiview projection example in third-angle drawing

Figure 13

14. Multiview projection example in third-angle drawing

Figure 14

15. Multiview projection example in third-angle drawing

Figure 15

16. Multiview projection example in third-angle drawing

Figure 16

17. Multiview projection example in third-angle drawing

Figure 17

18. Multiview projection example in third-angle drawing

Figure 18

19. Multiview projection example in third-angle drawing

Figure 19

20. Multiview projection example in third-angle drawing

Figure 20

15 Multiview Projection Examples (Front, Top, and Side Views)

Definition of multiview projection: what is multiview projection?

Multiview projection is the process of making parallel projections from different directions on two or more planes of a 3-D object.

The drawings produced by making multiview projection on a 3-D object can be first-angle drawing or third-angle drawing, which are both very popular. Second-angle drawing and third-angle drawing can also be produced; however, they are not as widely used as first- and third-angle drawings.

Generally speaking, multiview projection—a type or system of orthographic projection—can be used to create various types of 2-D views portrayed on technical, engineering, and architectural drawings (i.e., first-angle, second-angle, third-angle, and fourth-angle drawing, respectively).

The Planes of Projection in Multiview Projection

Each view or drawing produced from a multiview projection provides certain definite information which contributes to the overall detail concerning an object or structure.

Multiview projection examples (front, top, and side views) of different objects

The following 15 multiview projection examples show how the three principal views of different types of 3-D objects or structures are represented on technical, engineering, and architectural drawings, respectively:

1. Multiview projection example of an object (front, top, and side views)

Figure 1

2. Multiview projection example of an object in third-angle drawing (American system)

Figure 2

3. Multiview projection example of an in first-angle drawing (European system)

Figure 3

The 6 Principal Views of 3D Objects from Multiview Projection

15 Examples of the 6 Principal Views of Objects/Structures

4. Multiview projection example of a book in third-angle drawing

Figure 4

5. Multiview projection example in third-angle drawing

Figure 5

6. Multiview projection example in third-angle drawing

Figure 6

7. Multiview projection example in third-angle drawing

Figure 7

8. Multiview projection example in third-angle drawing

Figure 8

9. Multiview projection example in third-angle drawing

Figure 9

10. Multiview projection example in third-angle drawing

Figure 10

11. Multiview projection example in third-angle drawing

Figure 11

12. Multiview projection example in third-angle drawing

Figure 12

13. Multiview projection example in third-angle drawing

Figure 13

14. Multiview projection example in third-angle drawing

Figure 14

15. Multiview projection example with hidden lines in third-angle drawing

Figure 15

The Planes of Projection in Multiview Projection

The planes of projection in multiview projection technique are employed in producing multiview (mainly first-angle and third-angle) types of technical and engineering drawing.

In most cases involving the planes of projection in multiview projection, three views of an object or structure are usually drawn together with the features and dimensions representing the object.

It is important to note that as many as six views can be drawn to represent an object (especially the visible part), and more than six views may be required to illustrate both the visible and inner or hidden part(s) of an object.

The 6 Principal Views of 3D Objects from Multiview Projection

15 Examples of the 6 Principal Views of Objects/Structures

Each plane of projection helps to create a 2-D view which is the view that can be seen on the plane of projection with respect to or based on the features of the object.

It may be important to understand what the terms multiview projection and plane of projection are before listing and defining the different planes of projection that are commonly used in multiview projection:

Definition of multiview projection: what is multiview projection?

Multiview projection is the process of making parallel projections from different directions on two or more planes of a 3-D object. The drawings produced by making multiview projection on a 3-D object can be first-angle drawing or third-angle drawing, which are both very popular. Second-angle drawing and third-angle drawing can also be produced; however, they are not as widely used as first- and third-angle drawings.

Generally speaking, multiview projection, which is a type or system of orthographic projection, can be used to create various types of 2-D views portrayed on technical, engineering, and architectural drawings (i.e., first-angle, second-angle, third-angle, and fourth-angle drawing, respectively).

Each view or drawing produced from a multiview projection provides certain definite information which contributes to the overall detail concerning an object or structure.

What is a plane of projection?

A plane of projection is a two-dimensional plane on which the shape of an object or structure is projected. The two-dimensional plane is only imaginary—i.e., it exists only in the imagination for the purpose of capturing the shape or image of objects or structures from different directions of lines of sight.

The line of sight on any plane of projection is an assumed or imaginary line of sight between the eye of the person observing an object and the object itself.

All lines of sight are parallel and don’t converge in multiview projection which is a type of orthographic projection that employs parallel projection; however, the lines of sight in perspective projection start at a single point and move towards an object, or converge at a single point away from an object. It is possible to apply the line of sight on an object, with or without the physical presence of that object.  

The different planes of projection in multiview projection help to represent or outline the features of 3-D objects or structures in many 2-D views on paper or computer screen.

The planes of projection in multiview projection

1. Frontal plane of projection

The frontal plane of projection is an imaginary two-dimensional plane on which the chosen front view of an object or structure is projected by the lines of sight with respect to the chosen front view.

Usually, the front view of an object shows the dimensions of height and width, but the choice of front view depends on the observer. The views in Figures 1 and 2 are front views.

Figure 1: The frontal plane of projection in multiview projection is used to capture the projected front views of objects

Figure 2: The front view drawn on paper or computer screen shows part of a 3-D object in 2-D (It’s not possible to show the depth or breadth because that part of the object is perpendicular to paper or computer screen.)

2. Horizontal Plane of Projection

The horizontal plane of projection is an imaginary two-dimensional plane on which the top view of an object or structure is projected by the lines of sight proceeding directly from above onto the top of the object or structure. Usually, the top view of an object shows the dimensions of width and depth (Figure 3).

Figure 3: The top view of an object is created by projecting its features onto the horizontal plane of projection

3. Profile Plane of Projection

The profile plane of projection is an imaginary two-dimensional plane on which the right side view of an object or structure is projected onto the right profile plane of projection which is parallel to the right side of the object (Figure 4). Whenever necessary, the left side view can be projected on the left profile plane of projection. The side views of an object usually show the height and depth dimensions.

Figure 4: The right side view of the object is created by projecting its features onto the right profile plane of projection

4. All planes of projection

Three main views are individually projected at a time onto three different planes of projection (frontal, horizontal, and profile plane) as shown together in Figure 5.

The top view is usually located above and aligned with the front view, while the right side view is usually located at the right side of but still aligned with the front view.

Figure 5: Multiview projection (i.e., projection on most or all planes) helps in creating the front, the top, and the right side in an instant

15 Examples of the 6 Principal Views of Objects/Structures

The following 15 examples show how the six principal views of different types of 3-D objects or structures are represented on technical, engineering, and architectural drawings, respectively:

1. Example of 6 principal views of a house

Figure 1 below shows the views (the front, the top, the right side, the left side, the rear, and the bottom) that can be seen from different locations around a house, and the corresponding six principal views or multiview. Imagine the top view being seen by looking down from an airplane and the bottom by looking up from a worm’s eye-view underneath the house. The term plan can also be used in place of top view, and the term elevation applies to all views that show the height of a house or any object.

Figure 1: Six principal views of a house

2. Example of 6 principal views of a car

Figure 2 shows the 3-D view of a car (produced from axonometric projection or oblique projection) and the six principal views produced by making six different projections through the six mutually perpendicular planes of projection.

Figure 2: Six principal views of a car

3. Example of 6 principal views of a part of an iron pipe fixed in a concrete foundation

Figure 3 shows an object and six principal views produced by making six different projections through the six mutually perpendicular planes of projection.

Figure 3: Six principal views of part of an iron pipe fixed in a concrete foundation

4. Example of 6 principal views of a structure for suspending cars from the ground in a mechanic’s workshop

Figure 4: Six principal views of a structure for suspending cars from the ground

5. Example of 6 principal views of part of a culvert

Figure 5: Six principal views of part of a culvert

6. Example of 6 principal views of part of a concrete wall

Figure 6: Six principal views of part of a concrete wall

7. Example of 6 principal views of part of a staircase

Figure 7: Six principal views of part of a staircase

8. Example of 6 principal views of part of a machine

Figure 8: Six principal views of part of a machine

9. Example of 6 principal views of a fabricated steel object

Figure 9: Six principal views of a fabricated steel object

10. Example of 6 principal views of a wooden structure

Figure 10: Six principal views of a wooden structure

11. Example of 6 principal views of part of a concrete column

Figure 11: Six principal views of part of a concrete column

12. Example of 6 principal views of part of a large industrial equipment

Figure 12: Six principal views of part of a large industrial equipment

13. Example of 6 principal views of part of a reinforced concrete wall

Figure 13: Six principal views of part of a reinforced concrete wall

14. Example of 6 principal views of part of the wall and adjoining foundation of a swimming pool

Figure 14: Six principal views of part of the wall and adjoining foundation of a swimming pool

15. Example of 6 principal views of a mechanical device

Figure 15: Six principal views of a mechanical device

The 6 Principal Views of 3D Objects from Multiview Projection

The multiple views or multiview of objects illustrated on different types of technical, engineering, and architectural drawings respectively are produced from projections, of which there are different types and subtypes: parallel projection (four subtypes: orthographic projection, oblique projection, multi-view projection, and axonometric projection) and perspective projection (two subtypes: aerial perspective and linear perspective).

Definition & Types of Technical Drawing (PDF Download Available)

By making parallel projections from different directions on different planes of a 3-D object, one can completely describe the shape of the object by illustrating the different views on a drawing.

Definition of multiview projection: what is multiview projection?

Multiview projection is the process of making parallel projections (the technique employed in orthographic projection) from different directions on two or more planes of a 3-D object. The drawings produced by making multiview projection on a 3-D object can be first-angle drawing or third-angle drawing, which are very popular. Second-angle drawing and third-angle drawing can also be produced, but they aren’t as widely popular as first- and third-angle drawings.

Generally speaking, multiview projection (which is a subtype or system of orthographic projection) results in different types of 2-D views portrayed on technical, engineering, and architectural drawings: first-angle, second-angle, third-angle, and fourth-angle drawing, respectively.

Each view or drawing from multiview projection provides certain definite information which contributes to the overall detail concerning an object or structure.

The six principal views of an object

As shown in Figure 1, any object or structure can be viewed from six different directions that are mutually perpendicular. The different directions give rise to and are called the six principal views of an object; they shall be defined later in the post: front, top, left side, right side, bottom, and rear.

Figure 1: Six principal views of an object—a 3D object

Although six principal views are very common in drawing practice, it may be important to note that the plane of projection (i.e., the direction in which parallel projectors or rays are projected on an object) can be oriented or changed to produce an infinite number of views of any object.

However, some views are more important and widely used than others. The most important views are the six principal views which are all mutually perpendicular views produced through six mutually perpendicular planes of projection.

Figure 2 shows the 3-D view of an object (which could be a drawing produced from either axonometric projection or oblique projection) and the corresponding front view drawing produced from making a projection on the front view of the object—or 3-D object; a total of six principal views can be produced by making five other different projections through the remaining five mutually perpendicular planes of projection.

Figure 2: Front view of the 3-D object

Figure 3 shows a drawing that consists of multiple views or the six principal views produced by making multiview projection on different parts of an object. Usually, the surfaces of the object are shown in their true size and shape.

Figure 3: Multiview or 6 major views of a 3D object

The easiest way to make a multiview projection, mentally or in one’s imagination, is by using the Glass Box Method which involves suspending an object in a glass box in such a way that the respective positions of the object’s major surfaces are parallel to the sides of the box. Consequently, the six different sides of the box can be used individually as projection planes to help illustrate the six principal views (Figure 4).

Figure 4: Glass Box Method involves suspending an object in a glass box and using the six different sides of the box individually as projection planes to help illustrate the six principal views

Definitions of the six principal views (front, top, left side, right side, bottom, and rear views respectively):

1. The front view

The front view is one of the six principal views that shows most of the important features or characteristics of an object. The other remaining five views are based on the part of an object that has been chosen as the front view.

2. The top view

The top view is one of the six principal views that shows the top of an object after the front view has been chosen. In many cases, likely in all cases, the top view is part of the object that can be seen by looking downward at the object from the sky.

3. The right side view

The right side view is one of the six principal views that shows the right side of an object after the front view has been chosen.

4. The left side view

The left side view is one of the six principal views that shows the left side of an object after the front view has been chosen. In many cases, especially when the hidden or inner features of the object appear the same from all directions, the left side view is the mirror image of the right side view.

5. The rear view

The rear view is one of the six principal views that shows the rear part of an object after the front view has been chosen. Usually, the rear view is 90 degrees toward the left side view and is a mirror image of the front view, especially when the hidden or inner features of the object appear to be the same from all directions.

6. The bottom view

The bottom view is one of the six principal views that shows the bottom of an object after the front view has been chosen. The bottom view is a mirror image of the top view, except when the hidden or inner features of the object do not appear to be the same from all directions.

To gain insight on how to draw the above six principal views on any 2-D media such as drawing paper or computer, mentally unfold the glass box to imagine how the views would look like, then proceed to draft the views as shown in Figure 5.

Figure 5: Unfolding the glass box to produce a drawing that has six principal views

Advantages of Multiview Projection

Multiview projection is used in technical, engineering, and architectural drawing, respectively, to show one or more important views of an object or structure. Multi-view projection is actually a projection of many orthographic projections or views all on one place or media such as paper or computer screen.

In multiview projection, the parallel projectors are directed perpendicularly in the plane of projection toward the major planes or most important parts of an object such as the top, front, and side views (and may include other important sides) of an object which are all drawn or represented in 2-D.

Most drawings show a minimum of three or four views; others show more, up to a maximum of six views (top, front, right-side, left-side, rear, and bottom). The required number of views may even be more than six if sections are required to show the inner parts or details of an object or structure. Generally, the views in any drawing are illustrated with reference to the direction of the planes of projection with respect to the object.

Multiview projection can be employed in creating at least two (or up to four) types of technical, engineering, or architectural drawing: first-angle drawing and third-angle drawing. Note that second-angle and fourth-angle drawings are either not widely used or not used at all in different parts of the world.

13 Types of Engineering Drawing (Free PDF Download Available)

Apart from multiview projection, four other main projection methods can also be used to produce various kinds of technical, engineering, or architectural drawing:

• aerial (perspective) projection: used to produce aerial drawing.
• linear (perspective) projection: used to produce one-point, two-point, and three-point drawing, respectively.
• axonometric (parallel) projection: used to produce isometric, dimetric, and trimetric drawing, respectively.
• oblique (parallel) projection: used to produce cavalier and cabinet drawing, respectively.

However, multiview projection has a great advantage over other projection systems, especially when it comes to manufacturing or producing real-life objects or structures from technical, engineering, and architectural drawings.

To produce a new product from a drawing, the true dimensions have to be known; however, the dimensions provided by or illustrated on most drawings produced from axonometric, oblique, pictorial or perspective (aerial and linear respectively) projection are mostly distorted or foreshortened. Working with them may cause misunderstanding and take or waste time.

To make the point clearer, take a look at Figure 1 which shows a photograph or pictorial perspective image of a road, exactly how it was captured on camera. Notice how the white poles and trees that are further away, appear shorter and closer together the more distant they are away from the camera.

Figure 1: Perspective image of a road, including some other objects/features

As good as the image looks, it doesn’t provide actual or true distances, the type required in constructing or manufacturing real-life objects or structures such as roads, electricity poles, etc. The advantage multiview projection has over pictorial perspective image or projection is its quality of illustrating more than one important view, along with true distances, measurements, dimensions, widths, breadths, angles, etc., regardless of the scale ratio used on the drawing.

Figure 2 illustrates how the lines of sight on the front and side views, respectively, in perspective projection distorts the real dimensions or measurements. By using a ruler to take measurements, notice how the two different width dimensions in the front view for the top of the block are different in length—they appeared to be different, even before measurement.

Figure 2: Perspective drawings distort true linear dimensions

Once again, as demonstrated in Figure 2 and supported by Figure 1, the main advantage of multiview projection over pictorial perspective image or projection is in its illustration of true distances, instead of distorted distances which is one of the main properties of perspective (aerial and linear), axonometric, and oblique projections, respectively.

In axonometric projection, the parallel projectors are directed perpendicularly towards any plane of a 3-D object that is tipped or rotated about one or more of its major axes (x, y, and z) to show different sides (top, side, and front views, etc.). This results in a projection that is usually expressed in a single view with some foreshortened or distorted dimensions.

Measurements are foreshortened or distorted as demonstrated by the axonometric projection in Figure 3; angles are distorted in the isometric drawing (produced from axonometric projection) in Figure 4 where right angles (which are actually supposed to appear as 90 degrees) do not appear as 90 degrees, and real circular holes appear as ellipses, instead of circles.

Figure 3: Axonometric projection with foreshortened or distorted measurements or dimensions (Image credit: Peachpit.com.)

Figure 4: Isometric drawing with distorted circles and angles (or angular dimensions), instead of true circles and angles

The advantage that multiview projection has over axonometric projection is in its quality of illustrating real angles and measurements that are not foreshortened or distorted.

In oblique projection, the projectors are parallel to each other but not perpendicular to any planes of the 3-D object they are projected on, and one of the three planes of the object is projected at either 30°, 45°, or 60° to the x-axis. Angle 45° is used in most oblique projections. Since the parallel projectors are not projected perpendicularly on any 3-D object’s plane, oblique projection results on drawings that have true shapes and sizes on ONLY one or two planes/faces—not all planes/faces like drawings produced from multiview projection.

Figure 5: Oblique projection for an object (Image credit: Slideplayer.com.)

In other words, in oblique projection or view, true shapes and sizes are illustrated by only the front surfaces and the surfaces that are parallel to the front surface. In drawings produced from oblique projection (such as cavalier and cabinet drawing, respectively), circles also appear as ellipses, except at the front plane and the surfaces that are parallel to the front surface.

The advantage of multiview projection over oblique projection is its quality of illustrating or providing true distances, measurements, dimensions, angles, widths, breadths, etc.

Concluding remarks

The true sizes and dimensions of an object or structure can be represented in multiview or more than one view if the object or structure is correctly positioned relative to the projection planes.

Since so many activities in engineering, technology, and architecture depend on the exact shape, size, and descriptions illustrated on drawings, the best approach would be the parallel projection technique called multiview orthographic projection which can create different views that individually show a combination of a combination of only two of the three main dimensions: height, width, and depth.

Multiview projection—through the consequent first-angle and third-angle drawings produced from it—provides the most accurate illustration of 3-D objects and structures for construction, manufacturing, and engineering requirements—demonstrating true-size features which are useful in creating dimensionally accurate parts.

Constraint-based Modelling Software: Standard Features or Commands

Common features of constraint-based modeling software features, respectively, were developed from specific real-life manufacturing processes; as a result, many engineering models and designs consist of certain practicable features. 

For instance, the counterbore process is often applied in manufacturing to make or construct a recess for a fastener or bolt head. The counterbore tool in milling machines is used to enlarge the upper part of holes when producing many kinds of machines or equipment.

Constraint-based modelling softwares consist of not only the built-in counterbore standard feature or command, but other built-in standard features or commands for different purposes.

Some constraint-based modelling software features are solids (or positive solids), while others are negative solids. Negative solids are solids or volumes of space that are usually subtracted from models; for example, when creating a cylindrical hole in an object or structure.

The standard features consist of properties that have been programmed and can be utilized by commands created by constraint-based modellers. The commands provide various options for quickly creating holes and carrying out other very important functions, in the same vein as it happens during real-life manufacturing.

On the broader scheme of things, many modelling softwares have commands often used to create forms or nonstandard features (i.e., features that aren’t built-in or part of the program that runs the modelling software) in many engineering designs.

The figure below shows important features of the manufacturing process; they are utilized in similar fashion in constraint-based modelling softwares to easily create models via commands.

Figure: Common features of manufacturing processes also used as commands in constraint-based modelling softwares

Many constraint-based modeling programs use the same terminologies that apply to features or aspects of manufacturing and design. The standard features and commands used in constraint-based modelling are as follows:

1. Boss

Boss is a standard feature indicating a projection or extrusion that is raised above the surface of part of an object or structure. As a command in constraint-based modelling, it is used to create or provide a solid flat bearing surface.

2. Bushing

Bushing feature or command functions as a hollow cylinder, oftentimes used as a bearing, or as a protective guide or sleeve.

3. Chamfer

Chamfer functions as an angled surface that makes it easier to work around plates and start creating holes on cylinders.

4. Counterbore

As explained earlier (in regard to real-life manufacturing process), counterbore creates or provides cylindrical recess around a hole, usually to prepare an opening for the entrance of a nut or a bolt head.

5. Countersink

Countersink provides or creates a cone-shaped recess around a hole, usually to prepare an opening to receive a tapered screw head.

6. Fillet

Fillet functions as a fastener that consists of a narrow piece of welded metal and is rounded on the edge formed where two steel surfaces or members are joined together. Fillet is generally used to strengthen adjoining surfaces or remove a part from a model. Usually, a fillet is created by choosing the edges that have to be filleted, and defining the fillet’s radius.

7. Flange

Flange functions as a flattened rim or collar used around a cylindrical component to enable attachments to be made between parts or objects, wherever necessary.

8. Keyseat/keyway

Keyseat is utilized on the axis of any cylinder in the form of a shaped depression for the entrance of a key or to attach gears, hubs, and other features to a cylinder in such a way that they won’t be able to turn on it.

9. Knurl

Knurl provides stronger gripping on a surface and increases the surface area for objects or parts to be attached. It is usually employed on tool handles and knobs.

10. Lug

Lug functions as a rounded or flat short strip of material projecting from a surface to facilitate opening, handling, or allow attachments between parts or objects.

11. Neck

Neck functions as a channeled cut around the diameter of a cylinder, usually where there is a change in diameter.

12. Round

Round is a standard feature that is created in the same way, usually using the Fillet command which was defined earlier. Round functions as a rounded exterior merger between surfaces and is used to make corners and edges easier to work around, especially during manufacturing.

13. Spotface

Spotface creates a shallow recess like counterbore does; it is used to provide effective bearing surfaces for fasteners.

Guidelines for Correct & Incorrect Dimensioning Practices in Drawings

Generally, sound judgement should be employed when dimensioning or placing dimensions on technical and engineering drawings. The drawings in the figure below show correct (preferred or widely used) and incorrect dimensioning practices in drawing.

Figure: Correct and incorrect dimensioning practices

Standards or basic rules are adhered to when placing dimensions; however, there may be situations in real life or practice whereby it would be impossible to follow standards or the rules.

Therefore, whenever one finds themself in a situation where they have to break or not adhere to a dimensioning principle or rule, they should wisely use sound judgement and above all maintain clarity and cohesiveness—everything should stick together.

The following guidelines are best practices for correct dimensioning—to prevent incorrect dimensioning:

1. Do not cross extension lines; however, whenever you cross extension lines in a particular situation, do not break the extension lines.

2. Do not cross extension lines over dimension lines. Whenever you have to, especially when there is no other solution, break the extension line at the point where it crosses over the dimension line.

3. No matter what, never break a dimension line.

4. Break extension lines whenever they cross over or close to an arrow or arrowhead; this practice is usually applied when an extension line crosses a leader line close to the arrowhead. In other cases different from this, it isn’t necessary to break an extension line. Computer-aided design (CAD) may not allow users to break extension lines. This can be confirmed from CAD instructions.

5. Do not apply dimensioning through or over the drawings of objects or structures.

6. Do not apply dimensioning to drawings that concern hidden features.

7. Do not use unnecessarily long extension lines in drawings.

8. Do not use any line of the drawing of an object as an extension line.

9. Apply dimensions or dimensioning between views whenever necessary and possible.

10. Group adjacent dimensions.

11. Apply dimensions and dimensioning to views that have the best shape description.

12. Do not use a visible object line, a centerline, a phantom line, and extension line, or a continuation of these lines as a dimension line.

13. Spread adjacent dimension numerals throughout the drawing area so they don’t line up closely together and prevent the drawing from being easily understood or interpreted.

3 Main Aspects of Good Dimensioning in Drawings

Different types of geometric shapes such as cone, cylinder, sphere, prism, pyramid, and so forth are often used as parts of assembled engineering objects or structures, either as positive (exterior) forms or negative (interior) forms; for instance, a steel shaft is regarded as a positive cylinder, while a round hole on the other hand is regarded as a negative cylinder.

Geometric shapes are selected based on design necessity and suitability with manufacturing operations. Some aspects of good dimensioning are crucial to proper interpretation and production, especially in regard to forms that have plane surfaces and are usually produced by planning, shaping, milling, etc. Forms that have spherical, cylindrical, or conical shapes can be created or manufactured by reaming, countersinking, turning, boring, drilling, and other kinds or rotary operations.

Before we list the three main aspects of good dimensioning, there are two important steps to take note of when dimensioning technical and engineering drawings:

• Provide size dimensions: size dimensions are dimensions that define the sizes of objects, structures, or simple geometric shapes.
• Provide location dimensions: location dimensions are dimensions that define the respective locations of the elements of an object, structure, or geometric shape with respect to each other. Location dimensions locate not only surfaces; they also locate 3D geometric elements.

Good dimensioning is applicable to angles, heights, widths, and notes, regardless of the unit (Metric, Imperial, etc.) being used. Good dimensioned drawings, whether they are produced by computer-aided design (CAD) or hand drawing (i.e., traditional tools), give consideration to the following main aspects:

1. Technique of dimensioning

The standards adhered to in any technique of dimensioning should definitely make the appearance of features, lines, arrowhead size, dimension spacing, etc., clear and interpretable to whomever is reading the drawing.

Any typical dimensioned drawing that follows proper standards for dimensioning (or principles of good dimensioning) can be easily read or understood because of the obvious strong and clear relationship between the thin lines used in dimensioning an object and the object’s own visible lines.

2. Placement of dimensions

Any typical dimensioned drawing that follows proper standards for dimensioning, places or positions dimensions logically in formats that are readable or interpretable and in accordance with good or standard dimensioning practices. It’s very easy to assess how suitable a placement is when a dimension is placed between two views to see if and how the dimension is related to the object, structure, or feature shown on each different view.

3. Choice of dimensions

The choice of dimensions indicated on drawings affects how a product or design is manufactured. When dimensioning, it’s important to consider dimensions based on their function, and the dimensioning can be reviewed to see if improvements are needed to make manufacturing easier and still lead to the desired end result.

The choice of dimensions should include selection of functional dimensions or dimensions that can be understood by the manufacturer of the object or structure, as indicated on the drawing. Therefore, it is important to keep the following in mind:

• The end result or the final or finished piece.
• The function of each individual feature or part of any object, or the complete assembly of different parts.
• Making an assessment(s) of the end result or final piece to determine its suitability or acceptability.
• Manufacturing, production, or construction processes.

Principles of Good Dimensioning in Technical & Engineering Drawings

Dimensioning is a method used to give more life in technical and engineering drawings by accurately communicating the size and related information of objects, parts, features, or structures illustrated on the drawings.

Dimensioning of technical, mechanical, and engineering devices follows engineering drawing standards which are founded on standard dimensioning practices—the principles of good dimensioning—including the proper use and positioning of dimensions and dimensional information on technical and engineering drawings.

Unless principles of dimensioning are properly applied to both shape and size information, it will be difficult if not even impossible to turn design ideas into reality.

19 Principles of good dimensioning

Generally, “clarity” is the main principle of dimensioning everyone should practice above all else. Specifically, the principles of good dimensioning are but may not be limited to the following:

1. Each part or feature of an object or structure illustrated on a drawing is dimensioned only once: each dimensioned drawing shouldn’t have two or more interpretations.

2. Dimensions should be chosen based on the function of an object.

3. Dimensions should be positioned on the most informative view of a feature or part of the object that is being dimensioned.

4. Dimensions should specify only the size of a feature or part of an object or structure.

5. The angles shown on drawings as right angles are assumed to be 90 degrees except specified otherwise.

6. Dimensions should be located outside the boundaries of objects whenever possible.

7. Dimension lines should be lined up where possible to ensure uniform appearance and clarity.

8. Crossed dimension lines should be avoided whenever possible; if dimension lines must cross, then they should be unbroken.

9. The space between an object and its related first dimension line should be at least 3/8 inch or 10 mm, and the space between dimension lines should be at least 1/4 inch or 6 mm.

10. There should be a visible gap between the origin of an extension line and the object on a drawing.

11. Extension lines should extend beyond the last dimension line by 1/8 inch or 3 mm.

12. Extension lines that are close to or cross an arrowhead or arrow should be broken.

13. Any leader line used to dimension a circle or arc should be radial.

14. Dimensions should be positioned so they can be read from the bottom of the drawing.

15. Diameters should be dimensioned with a numerical value that is preceded by the diameter symbol ϕ which is the Greek letter phi.

16. Whenever possible, concentric circles should be dimensioned, longitudinally. 

17. Radii should be dimensioned with a numerical value that is preceded by the radius symbol R.

18. Whenever a dimension is assigned to the center of a radius or arc, a small cross that has thin lines should be indicated at the center.

19. Counter-bored, spot-faced, or countersunk holes should be specified in a note.

Dimensioning Terminology/Terms Used in Technical & Engineering Drawings

Dimensioning in technical and engineering drawings involves positioning dimensions and other extra graphical information on drawings to help clearly and concisely define the features, shapes, or sizes of the objects or structures illustrated on them.

Dimensioning terminology includes terms that refer to the individual purpose(s) or function(s) of the dimensions and other graphical information that gives greater expression to the features, shapes, or sizes of the objects or structures drawn on technical and engineering drawings.

Each dimensioning term reflects a function on technical and engineering drawings; for instance, there is a dimensioning term for features that define or locate holes, there is another for the center of circles, there is yet another for the distances between different planes of lines, and also another for the angles between different planes or lines, etc.

Adding dimensions and other extra graphical information that dimensioning terms refer to provides important details and makes drawings easily interpreted by anybody who knows how to interpret technical and engineering drawings.

Generally speaking, dimensioning terminology or terms represents features that help in producing/manufacturing drawn objects or assembling their parts, thereby eliminating any guesswork and uncertainty.

Figures 1 and 2 below provide a view of the most common dimensioning terms used in dimensioning on technical and engineering drawings.

Figure 1: Dimensioning terminology: 13 dimensioning terms

Figure 2: Datum dimensioning term

14 Dimensioning terms

The 14 dimensioning terms in Figures 1 and 2 are listed and defined as follows:

1. Arrow

Arrow is the dimensioning term that refers to any symbol positioned at the ends of dimension lines to signify the extent or limits of dimensions, cutting plane lines, and leaders.

Regardless of how big or small a drawing is, the arrows are uniform, usually about 3 mm or 1/8 inch long and have a width that is 1/3 its length. Figure 1 shows how the dimensions applicable to arrows look like when drawn by hand.

2. Basic dimension

Basic dimension is the dimensioning term that refers to any numerical value used to theoretically define the exact shape, size, location, orientation, or profile of a characteristic or feature relative to a coordinate system in regard to datums. Basic dimensions have no tolerance and can be identified on drawings by any dimension enclosed in a rectangular box.

3. Datum

Datum is the dimensioning term that refers to any point that is precise or accurate, at least theoretically speaking, and is used as a reference for tabular dimensioning, as shown in Figure 2 above.

4. Diameter symbol

Diameter symbol is the dimensioning term or graphic symbol that indicates a particular dimension is a diameter of a circle or circular hole. The diameter symbol usually precedes a numerical value that indicates a diameter of a circle. The symbol for the Greek letter phi (ϕ) is used on drawings to illustrate that a dimension represents the numeral value for a diameter.

5. Dimension

Dimension is the dimensioning term that refers to any numerical value used to define the location, shape, size, surface texture, or geometric features of an object or structure illustrated on technical and engineering drawings. Usually, each dimension text has a height of 3 mm or 0.125 inch with a 1.5 mm or 0.0625 inch space between the lines of the text.

6. Dimension line

Dimension line is the dimensioning term that refers to any thin line that expresses direction and magnitude or extent of a dimension. Dimension lines are usually broken in the middle to provide space for locating or positioning dimension numbers which are also known as numerical values.

7. Extension line

Extension line is the dimensioning term that refers to any thin line that is perpendicular to a dimension line and used to indicate features associated with a dimension.

8. Leader line

Leader line is the dimensioning term that refers to a thin line used to indicate features that a particular dimension, symbol, or note is associated with.

Leader lines are usually straight lines that are oriented at an angle that is neither vertical nor horizontal. Leader lines have an arrow at one end and a short horizontal shoulder at the opposite end.

9. Limit of size

Limit of size is the dimensioning term that refers to the maximum and minimum acceptable sizes, respectively, of an object’s feature(s). The numerical value for the largest acceptable size is usually indicated as the maximum material condition (MMC) and located over the numerical value for the minimum acceptable size which is indicated as the least material condition (LMC) and refers to the limit-dimension-based tolerance for an object’s feature(s).

10. Plus and minus dimension

Plus and minus dimension is the dimensioning term that refers to any allowable positive and negative variance of a specified dimension(s). Usually, the plus and minus dimensions or numerical values may or may not be the same.

11. Radius symbol

Radius symbol is the dimensioning term or symbol that indicates a particular dimension is a radius of a circle or circular hole. Usually, the capital letter R is the radius symbol.

12. Reference dimension

Reference dimension is the dimensioning term that refers to any numerical value that is enclosed in parentheses to only provide information that would not be used directly in fabricating the drawn object, structure, part, or feature. Older drawings or drawing standards may allow the REF text placed next to a reference dimension, instead of parentheses.

13. Tolerance

Tolerance is the dimensioning term that refers to the numerical value that a particular dimension is allowed to deviate or vary from. Tolerance is the difference between the maximum allowable limit and minimum allowable limits of variation.

Usually, all dimensions have an associated tolerance, except reference dimensions. Each tolerance can be expressed by a general note or through a limit dimensioning such as plus and minus dimension or dimensioning procedure.

14. Visible gap

Visible gap or “gap” is the dimensioning term that refers to the gap placed on drawings between the object’s or feature’s corners and the end of any related extension line. The visible gap is usually 1.5 mm or 1/16 inch.

Components or Elements of Dimensioning in Technical & Engineering Drawings

The measurements written around objects or structures to define them on technical/engineering drawings are called dimensions. But some extra graphical information still needs to be added to the dimensions to provide clear and concise information that can help in producing/manufacturing drawn objects or assembling their parts, thereby eliminating any uncertainty and guesswork. It is in this aspect of technical/engineering drawings that the components or elements of dimensioning are very useful; for instance, in defining or locating holes, the center of holes or circles, the distances between different surfaces, the angles between different lines, etc.

Before listing the components or elements of dimensioning, let’s understand what dimensioning means: dimensioning is the process of adding the different types of dimensions and components of dimensioning to the dimensions/numerals defining the sizes or shapes of objects or structures on technical and engineering drawings.

Adding the elements of dimensioning helps to provide details about the shape or size and positions of important parts of an object or structure by specifying or highlighting its physical parameters. The components or elements of dimensioning include lines, symbols (for example: ϕ, Ω, °, etc.), and gaps—it may even include notes, as practiced in some parts of the world.

The figure below provides a view of the most common components of dimensioning—also known as dimensioning components—with terminologies that correlate with common CAD (computer-aided design) dimensioning terminologies.

Figure: Standard dimensioning characteristics

For any drawing to be widely interpreted by people (especially those who are trained to interpret or produce technical and engineering drawings), information about all the necessary dimensions have to be provided so that objects or structures indicated on drawings can be accurately manufactured or produced in real life. To achieve this goal, the components or elements of dimensioning have to be used on technical and engineering drawings.

Types of dimensioning component or element

1. Angular dimension line

Angular dimension line is the type of dimensioning component represented by an arc that is centered from the vertex of the related angle and has arrowheads at its ends, as indicated in the figure (standard dimensioning characteristics) above.

2. Arrowhead

Arrowhead is the type of dimensioning component used to cap off or indicate the ends of dimension lines and leader lines.

20 Types of Engineering Drawing Lines and Their Uses

Types of Lines Used in Technical Drawing

3. Center dash

Center dash is the type of dimensioning component that is drawn as thin lines and used to dimension the center location or indicate a part of the centerline of a shape or object. Generally, center dashes are between 0.12 inches or 3 mm (millimeters) in length, height, or width.

4. Centerline space

Centerline space is the type of dimensioning component that indicates the space between the short dash and long dash elements of any centerline. Centerline space is usually 0.06 inches or 1.5 mm.

The centerline offset is the part of the centerline that extends beyond the center of the circle, square, shape or other related feature. The centerline usually extends by anywhere between 0.12 and 0.24 inches (i.e., between 3 and 6 mm).

5. Dimension line

Dimension line is the type of dimensioning component that is drawn as a thin line with arrowheads at its ends to indicate the length, height, or width of the dimension of an object or structure. Dimension lines are usually broken along their length to provide space for dimension numerals or numbers.

6. Dimension text

Dimension text is the type of dimensioning component that is a text usually 0.12 inches or 3 mm high and placed at the center or broken space on the dimension line.

7. Extension line

Extension line is the type of dimensioning component that is drawn as a thin line to indicate the extent of a dimension. Extension lines are offset by 0.06 inches or 1.5 mm from the object and extend by 0.12 inches or 3 mm beyond the last dimension line. 

8. Leader line

Leader line is the type of dimensioning component that is drawn as a thin line to connect a particular note to a feature on technical and engineering drawings. Generally, the leader line can be inclined at an angle between 15 and 75° (i.e., degrees), but 45° is mostly preferred.

Leader line can be attached to a short horizontal shoulder that should be anywhere between 0.12 and 0.24 inches (i.e., between 3 and 6 mm) and centered at the middle of any related text. When or where necessary, leader line can be used in combination with leader shoulder.

22 Best Types of Technical Drawing Pens

What is a technical drawing pen?

A technical drawing pen is any drawing pen that consists of a needle-tip, either a replaceable ink cartridge or a refillable ink reservoir, and waterproof ink which is used in creating consistently thick lines by freehand or together with most traditional technical drawing tools/equipment, and drawing, drafting, illustrating, or representing all kinds of objects or things, including technical, engineering, and architectural structures.

The use of technical drawing pens ensures that line thicknesses are consistent and drawings are precise. The term “technical drawing pen” is sometimes referred to as “technical pen” or just “drawing pen”.

Uses of technical drawing pens

Technical drawing pens are used to construct, draft, or produce artistic drawings by freehand and also technical, engineering, and architectural drawings by using drawing pens in combination with drawings tools or only freehand.

Technical drawing pens are used to create visually pleasing letters and font sizes. In engineering drawing, this process is called “lettering and/or type design” and is carried out successfully with the aid of templates and guides to draw/inscribe each letter on tracing paper or vellum.

Technical drawing pens are used in art, comic and illustration works to express the finest details of drawings that depict living and non-living things (objects, structures, entities, etc.).

Technical drawing pens are used by illustrators in the scientific and medical fields to produce detailed scientific and medical illustrations and represent subjects clearly and accurately. To ensure accuracy, illustrators often use a technique called stippling.

21 Best types of technical drawing pens

1. Brustro technical drawing pen

Brustro technical drawing pen is a waterproof and lightfast (i.e., resists fading when exposed to light) drawing pen that is used in combination with templates and rulers to create technical, engineering, and architectural drawings, and also for writing, sketching, and freehand technical drawing (fine art, anime, comics, illustration, design, details, papercrafting, journaling, and modelling). The ink in Brustro pen is fade-resistant, waterproof, and chemically stable, and does not smear or bleed through most kinds of paper.

2. Copic multiliner SP drawing pen

Copic multiliner SP is a sustainable type of technical drawing pen, designed for a lifetime with cartridges and nibs that can be easily exchanged. Copic Multiliner SP can be replaced when necessary; an even cheaper non-SP disposable Multiliner pen exists.

3. Deleter Neopiko Line-3 drawing pen

Neopiko Line–3 is a type of multiliner drawing pen that is smooth, lightfast, waterproof, and smudge-proof with water-based and alcohol-based markers, and is tailored to meet the needs of art students, illustrators, artists, professional artists, and graphic designers. 

4. Derwent Graphik Line Painter drawing pen

Derwent Graphik Line Painter is a technical drawing pen that consists of an opaque, lightfast, and permanent water-based pigment paint that is suitable for creating vibrant paintings, colorful line work, and illustrating strong color depth, even on backgrounds that are dark.

5. Edding 1800 Profipen drawing pen

The Edding 1800 Profipen drawing pen is a disposable pen that has waterproof, lightfast, and pigment ink and is ideal for freehand technical drawing, including illustration, anime, fine art, design, comics, etc. It is used by architects,  illustrators, cartographers, and designers and forms a good combination with stencils and rulers.

6. Faber-Castell Ecco Pigment drawing pen

Generally, Faber-Castell is well known for the Pitt drawing pen; however, the Ecco Pigment Liner is an alternative that’s just around the corner. It is lightfast, comfortable to use, high-grade, and consistent.

7. Faber-Castell Pitt drawing pen

The Faber-Castell Pitt pen is a technical pen that consists of water-resistant, lightfast, acid-free, odor-free, and pigmented ink and is used to produce vivid and thick lines on drawings. Like some other types of technical drawing pens, the Faber-Castell Pitt drawing pen is ideal for cartoonists, illustrators, and artists and their respective works.

8. Koh-I-Noor Rapidosketch drawing pen

Koh-I-Noor Rapidosketch technical pens are versatile pens that consist of water-proof ink and can be moved in all directions without the tip penetrating, digging, or snagging into drawing surfaces. Each Koh-I-Noor Rapidosketch pen has an ink reservoir that can be filled with Koh-I-Noor ink and a stainless steel nib that can be removed and cleaned.

9. Marvy Le Pen Drawing drawing pen

Mary Le Pen is a technical drawing pen that is lightfast and water-based, fast drying, non-toxic, smudge-resistant, acid-free, and non-toxic and can be used to create fine detailed technical drawings; is appropriate for manga, cartooning, comic, anime artwork, and even journaling.

10. OHTO Graphic Liner drawing pen

The OHTO Graphic Liner is a needlepoint technical drawing pen that consists of waterproof, archival, and strong black pigmented ink and a metal tip that protects the nib and prevents it from getting damaged over considerable time. OHTO Graphic Liner drawing pen can produce stable line widths throughout its lifetime; in addition, it won’t become dry if left uncapped for at least between 2 and 3 days.

11. Pilot Drawing Pen

The Pilot Drawing Pen is a technical drawing pen that consists of hard-wearing plastic tip and lightfast, highly water-resistant, and fast-drying black pigment ink which is ideal for drafting, illustration, sketching, and design works, owing mainly to its ability to be fast drying and highly resistant to light and water.

12. Rotring Isograph technical drawing pen

The Rotring Isograph technical drawing pen consists of a refillable ink reservoir and ink designed to help users to create flawless lines for exquisite detail work in technical, engineering, and architectural drawings/drafting and technical writing.

13. Rotring Rapidograph drawing pen

Engineers and draughtsmen have used both Rapidograph and Isograph Pens for many years to create lines that have consistent or constant width. Rotring Rapidograph is a steel-nibbed pen that has a replaceable capillary ink cartridge system and ink for drawing objects and structures on tracing paper, vellum, and lineboard.

14. Rotring Tikky Graphic technical drawing pen

Tikky Graphic employs Free Ink technology to create consistent lines; it is suitable for templates, straightedges, and many other types of technical drawing tools. Rotring Tikky Graphic drawing pen consists of water-resistant, durable, lightfast pigmented ink that has a unique deep black color and a clear ink-level window where the quantity of the remaining ink can be tracked. 

15. Sakura Pigma Micron drawing pen

Sakura Pigma Micron drawing pen is regarded in some quarters as the first disposable technical drawing pen. In fact it seems to be illustrators’ favorite by a mile, and for a convincing reasons, one which may be the smooth colors, writing, consistent lettering, and lines it leaves behind after use on each occasion.

16. Stabilo Fineliner Point 88 drawing pen

The Stabilo Point88 rollerball pen is one of the most popular technical drawing pens in the world; it is designed for drawings or sketches that involve fine contours. The Stabilo Point88 rollerball is smudge proof and mostly used for coloring, color writing, and illustrating, owing to its high-quality fineliner tip that is designed to create smooth and consistent lines.

17. Staedtler Pigment Liner technical drawing pen

The Staedtler Pigment Liner drawing pen is a high quality technical drawing pen that consists of lightfast and waterproof pigment ink. It is suitable for sketching, writing, and drawing or drafting, and can be used with rulers and templates.

18. Tombow MONO drawing pen

Tombow MONO drawing pen is a smooth pen. It consists of water-based odorless black pigment ink that creates smooth drawings and writings/lettering without smudging; its ink dries instantly. The Tombow Mono drawing Pen is highly suitable for cartridge papers and illustration purposes and is mostly used by artists who are passionate about the manga and comic industries.

19. Uni PIN Fine Line drawing pen

The Uni PIN Fine Line drawing pen consists of a water-resistant and fade-proof black super ink that is used to create different types of consistent line widths during drafting/drawing.

20. Winsor & Newton Fine Liner drawing pen

The Winsor & Newton Fine Liner is a technical drawing pen that has water-resistant ink and leaves incredible detail behind its trail whenever it is employed in sketching and drawing at all proficient levels.

21. Zig Mangaka drawing pen

The Zig Mangaka drawing pen is a technical drawing pen that has smudge-proof, lightfast, odorless, xylene-free, and water-based pigment ink. It is used by manga/cartoon artists, professional, and graphic designers, and is suitable for all technical drawing purposes, including lettering, sketching, drawing, journaling, form of art, etc.

22. Zig Millennium drawing pen

The Kuretake ZIG Millenium drawing pen consists of a fine fiber tip (enclosed in a long metal sleeve that is 6mm long) and odorless, water-based, acid-free, fade-proof, and waterproof ink that does bleed or penetrate through paper. ZIG Millenium drawing pen is suitable for use with squares and rulers in sketching, drawing, card making, etc.

21 Rules of Dimensioning in Technical & Engineering Drawings (PDF Available)

The dimensions illustrated on technical and engineering drawings abide by standards or rules of dimensioning by which physical variables are expressed, quantitatively. Dimensions include but may not be limited to: length, height, width, depth, or diameter of a technical or engineering object or structure.

Good technical and engineering drawings must have adequate information that can describe the complete shape or size of each object; for example: the location of circles or holes, the distances between surfaces, the type of material used, the nature of surface finishing, etc.

What is dimensioning?

Dimensioning is the process of following the rules of dimensioning to express the shape and size of engineering objects or features on a drawing by the use of lines, symbols, and figures.

Dimensioning can also be defined as the process of adding data/information about object size to a drawing: it is the process of inscribing or expressing the geometry (length, area, volume, etc.) or spatial shape and alignment of an object or feature through the use of numbers or numerical values.

In other words, dimensioning is the process of indicating dimensions or measurements and their respective magnitudes and directions, and the tolerance required for each on technical and engineering drawings.

In engineering practice, proper dimensioning enables workmen to create engineering objects or structures without having to calculate any sizes.

The importance of unambiguous and accurate dimensioning cannot be overemphasized. There are many cases in which improper dimensioning along with unclear or incorrect dimensions have caused premature structural failure and added considerable and unnecessary expenditure on fabrication of products.

Figure 1: Dimensioning of bearing housing

21 Rules of dimensioning

Technical and engineering drawing standards usually have a series of rules that promote good dimensioning practices. The rules of dimensioning are as follows:

1. Dimensioning should be done in such a way that the dimensions have only one interpretation, and no more.

2. No features of an object or part of an object should be defined by more than one dimension in any direction.

3. The angles indicated on technical and engineering drawings are assumed to be 90 degrees, unless they are specified in other terms; in addition, when no angle is specified, a 90-degree angle is used where center lines and lines displaying features are shown on 2-D drawings at right angles.

4. Only a necessary and minimum number of dimensions should be indicated to define an object, structure, or part on technical and engineering drawings: not more than the necessary dimensions should be used to completely define drawings, and the use of reference dimensions should be minimized on drawings.

5. Dimensions should be placed outside the outline of objects, structures, or views on drawings and there should be a minimum spacing between each object, structure, or view and the dimension or dimensions defining it. It is important to note that the smaller the spacing, the more difficult it will be to read or interpret drawings. A visible gap should be placed between the end of any extension line and the feature it defines or refers to.

6. Dimension lines should be placed on the view that illustrates the features they define. In other words, dimensions should be placed on the view that most clearly describes the feature that is being dimensioned.

7. Dimension and projection lines should be continuous thin lines which are also used to represent leader lines, extension lines, hatching lines for cross sections, reference lines, imaginary lines of intersections, and short center lines.

8. Avoid dimensioning hidden lines because they provide less clarity than visible lines: dimensions should be taken from visible outlines instead of hidden lines.

9. The center line of features or parts should not be used as a dimension line.

10. Any circle should be dimensioned by its diameter, across the circle or by projecting its diameter outside the outline. The dimension of the circle must be preceded by the symbol ϕ which means diameter. Generally, diameters, radii, squares, spotfaces, counterbores, countersinks, and depths should be specified with the appropriate symbol preceding the numerical value. Radius is dimensioned using the dimension line. The symbol R is used to precede the numerical value of the radius.

Download PDF: 21 Rules of Dimensioning in Technical & Engineering Drawings

Dimensioning & 7 Types of Dimensions in Technical Drawing

Types of Technical Drawing Lines and Their Uses

11. The dimension line to illustrate an angle should be a circular arc that has its center on the point about which the angle is orientated. The dimension should be located in such a way that it can be read from the bottom or right-hand side of the drawing.

12. Each feature of a technical or engineering object or structure should be dimensioned only once on a drawing.

13. Dimensioning should not be done on hatched areas, and dimensions should be placed on views or sections that clearly and closely relate to the corresponding features.

14. The same unit of measurement in measurement systems should be used for all dimensions on technical and engineering drawings, especially related drawings. In other words, the same unit should be used for all dimensions.

15. Dimensioning on objects or products should not include or specify manufacturing methods: manufacturing methods should not be specified as part of dimensions, unless no other method of manufacturing is acceptable. It may be important to note that specification of inappropriate manufacturing methods can cause unnecessary expenses and legal proceedings in court.

16. Numerical values should be used to specify dimensions for materials usually manufactured to gauges or code numbers which can be shown in parentheses, following numerical values.

17. Unless specified in other terms, it is assumed that all dimensions apply in a free state condition except for non-rigid parts. Free state condition refers to any distortion that takes place after the forces applied during manufacturing have been removed or ceased to operate. Non-rigid parts are parts that may have dimensional change because of thin wall characteristics.

18. The leader lines for radii and diameters should be radial lines—i.e., lines that relate to, move along, or have the direction of a radius.

19. A zero basic dimension should be used where center planes, axes, or surfaces are illustrated over each other on geometric controls and drawings to establish the relationship between essential features.

20. Unless specified in other terms, it is assumed that all dimensions and tolerances are measured at 20°C (68°F). However, compensation can be made for measurements taken at other temperatures.

21. It is assumed that any coordinate system shown on technical and engineering drawings is right-handed, unless specified in other terms. Each axis of the coordinate system is labelled in the positive direction. Right-handed implies that the coordinate system is in the clockwise direction.

Figure 2a is an example that illustrates incorrect dimensioning or violations of some of the rules of dimensioning in technical and engineering drawings. Figure 2b, on the other hand, illustrates correct dimensioning.

Figure 2a (Incorrect dimensioning) and Figure 2b (Correct dimensioning)

Reasons for the violations of some of the rules of dimensioning in Figures 2a and 2b

1. The dimension in 1 (i.e., 54) should follow the symbol (i.e., ϕ)—i.e., it should be ϕ54, not 54ϕ.

2/3. As much and far as possible, the features shouldn’t be used for dimensioning as extension lines.

4. The extension line should touch the feature instead of only being so close to it.

5. The extension line should project beyond the dimension line.

6. The dimension is not properly indicated as per the aligned system.

7. Hidden lines should intersect without any space.

8. The center line is wrongly represented, as a small dash should be used in place of a dot.

9. The horizontal dimension line should not be divided in that manner just to insert the value of the dimension.

10. The dimension should be placed above the dimension line, not below.

11. The radius symbol should be placed before the dimension, not after.

12. The center lines should cross each other at long dashes.

13. The dimension should be written beside a symbol, not beside an abbreviation.

14. Notes should be written in capital letters if they have a dimension.

15. Elevation is not the correct or appropriate term, as it is not specific.

16. The use of the term ‘‘plan’’ may not be appropriate because it depends on where one is taking a view or making a projection. More appropriate terms may be “view from above”, “view from front”, etc.

Conclusion

When dimensioning to create a properly illustrated object, structure, or feature, place the dimensions in such a way that they can be clearly viewed. If you need to, at a later time you can modify, change, or clean up the appearance of the dimensions to follow standard drawing practices.

Good dimensioning and dimension placement practices such as placing dimensions outside the outline of objects or structures and keeping them at a reasonable distance from one another will make it easier for your drawings or models to be understood or interpreted.

Applications of Engineering Graphics

Many people use the term “engineering graphics” in place of “engineering drawing” and vice versa. However, in today’s world, engineering graphics can hardly be mentioned without acknowledging, citing, or mentioning CAD (computer-aided design/drafting).

Engineering graphics can be defined as the detailed visual representation of one or more perspectives of engineering objects, structures, ideas, or concepts by use of engineering drawing tools & instruments or freehand.

This post provides a list of eight applications of engineering graphics by CAD—i.e., computer-aided engineering graphics—which is different from and has seemingly better advantages than engineering drawing or graphics by traditional tools.

Both engineering drawing by traditional tools and engineering graphics by CAD employ the components of the codes of practice when making illustrations or representations for engineering structures, ideas, or concepts.

Specific applications of engineering graphics by CAD are—but may not be limited to—the following:

1. Generally, computer-aided or digital engineering graphics make it easy to draw, visualize, and illustrate or depict engineering objects or structures, even more quickly and easily than engineering drawings via hand or traditional tools. For instance, digital engineering graphics are used to create and illustrate or depict the standard schematic representations of gears and detail representations of gear teeth more quickly and easily than engineering drawings would via hand or traditional tools.

One-half of the gear tooth can be drawn by using traditional techniques, while the other half can be drawn using the MIRROR command in CAD. The remaining teeth can be added to the root circle by using the COPY ROTATE command to copy the gear tooth a fixed number of times in a circular array.

CAD software can prompt users for essential information (such as the number of teeth, pressure angle, and pitch diameter, etc.) and proceed to automatically create the detail drawing of the specified gear.

Aside from gears, engineering graphics can be used in electrical and electronic drafting, respectively, in the form of symbols to illustrate or depict the components of schematic diagrams which consist of a series of lines and symbols that represent the components of the circuit and electrical current path and provide the circuit connection information for electrical and electronic products.

In contemporary times (as at the time of writing), engineers save a lot of energy by using computer-aided engineering graphics to approach engineering drafting problems and draw and illustrate many complicated geometric characteristics (for example: compound curves, arcs, the projection of engineering components such as screws, etc.) in a systematic manner that can help convert engineers’ ideas into formal graphic drawings or representations that are accurate and drawn to proper engineering drawing standards.

Engineering graphics by CAD gives one the ability to easily see interferences and clearances and quickly transfer information about interferences to drawings, thereby helping to eliminate many errors that may occur if only drawings are used.

2. Engineering graphics by CAD can sufficiently replace traditional tools in the construction and representation of cam profiles and displacement diagrams: once some critical information about the profile is entered into CAD software, the DISTANCE command can measure distances, the DIVIDE command can automatically divide lines into equal number of parts, and the SPLINE or curve fitting command can draw irregular curves. Examples of such critical information include the following:

• cam motion
• type of follower
• total displacement
• specific dimensions for the shaft, hub diameter, base circle, prime circle, etc.

3. Engineering graphics through CAD database (which provides technical information) helps not only engineers and design teams, but also helps the manufacturing, marketing & sales, and training departments respectively to communicate many kinds of verbal, visual, and quantitative information; in addition, it helps in simulation & analysis, production of engineering products using concurrent engineering practices, publications and training—all of these activities depend heavily on the graphical display of information.

Generally, computer-aided engineering graphics can be used to simulate and analyze engineering objects or structures in order to identify design flaws during the design process and make improvements in design, thereby ensuring safety and structural integrity and preventing failures or problems in the future.

Definition of Engineering Graphics, and Graphical Engineering

What Engineering Graphics and Design is all About

Basic Components of Engineering Graphics—the Code of Practice

4. Computer-aided engineering graphics can be utilized in virtual reality (VR) and simulation software tools to drastically slash down product development costs by eliminating expensive physical prototypes in product development planning organizations or collaborative visualization systems/departments where different technical and nontechnical groups share information in a graphic format to improve the respective levels of marketing, sales, training, design, and manufacturing.

Although VR tools have historically been the domain of researchers, the commercial applications of engineering graphics are becoming more common in automotive, aerospace, and medical device manufacturing where manufacturers can review realistic virtual model prototypes and gain insight to avoid certain costly expenses. Virtual reality systems like the computer automated visualization environment (CAVE), which was developed in the early 1990s, made it possible for automakers and aircraft manufacturers to review realistic virtual model prototypes and avoid the expense of $200,000 for a fiberglass auto prototype and to upwards of $3 million for an aircraft prototype.

Therefore, engineering graphics can be used in intensive research to hasten the development of emerging technologies and, in the process, help to further develop the spatial, imaginative, and multi-disciplinary research skills of everyone involved; in addition, it can help to uncover alternative approaches for creating models, making more appropriate/efficient designs, improving construction methods, cutting down costs, and yielding better outcomes in the spheres of product development and innovative design projects respectively.

5. Engineering graphics by CAD 3-D surface model can help users to efficiently and accurately develop multiview drawings by using a variety of techniques, depending on the engineering objects or structures of interest, one’s working preference, and information about the size and shape of the engineering objects or structures of interest.

In most cases, a combination of CAD engineering graphics tools and construction methods has proven to be the most effective way to produce multiviews which can also be created by extracting 2-D views from existing 3-D models. The extraction of 2-D views from 3-D models to create multiviews is a CAD engineering graphics technique or approach that is different from the traditional techniques of constricting multiviews; however, it still abides by the same multiview theory and format.

Three-dimensional CAD packages have options and engineering graphics tools that allow users to extract a variety of sectional views from a model. For instance, the SECTION VIEW tool allows users to section or create a sectional view by referencing an existing drawing view that is associated via some parameters. Sectioning is the part of CAD packages that helps to: 

• section and graphically visualize the shape of internal features
• clearly display designs
• create stylized model views
• work with complex assemblies and multiple components
• visualize assembly component relationships.

6. Computer-aided engineering graphics help to determine whether an engineering drawing needs to be modified; furthermore, it helps to modify drawings. For instance, it can help in studying and determining whether a multiview drawing needs an auxiliary view in order to show the angled face in its true shape and size, to study and analyze for better outcomes.

It may be important to point out that auxiliary views are used to depict or illustrate the true size and shape of a surface that is not parallel to any of the six principal views. The reasons for using auxiliary views may include but not be limited to the following:

• to find the actual length of a sloping line
• to find the actual shape and size of an inclined surface
• to find the point view of an inclined line
• to view objects in a different plane that is not one of the major principal planes: to view the object in another way or start successive auxiliary views.

A CAD engineering graphics tool such as AUXILIARY VIEW enables users to create an auxiliary view(s) by referencing an existing drawing view to associate a view with the model through certain parameters.

7. Computer-aided engineering graphics can be used to observe how the assembled components of an engineering object, structure, or drawing interact with each other; moreover, it can help to produce several types of assembly drawings, depending on one’s goal or the standard used by the company overseeing the drawings or graphic representations of engineering objects.

The seven applications of modern-day computer-aided engineering graphics listed above are widely employed in various fields, but may not be limited to:

• Aerospace: flight simulation, spacecraft design, lofting.
• Architecture: interior decoration, town planning, multistory complex design.
• Automotive industry: hydraulics, kinematics, steering.
• Civil/environmental engineering: structural design, mapping, building drawing, contour plotting.
• Communication: TV telecasting, satellite transmitting pictures, communication network.
• Electrical/electronic engineering: panel design, circuit layout, control systems, schematic diagrams of PCs, ICs, etc.
• Mechanical engineering: robotics, design of machine elements, CNC machine tools.

Principles of Engineering Drawing Appropriate for Infrastructure Projects

Civil and environmental engineers design infrastructures that will eventually be constructed in real life, even if they won’t partake in the construction projects themselves. 

The principles of engineering drawing are important to civil and environmental engineers because they are invariably at the receiving end of drawings, just like engineers in other fields of engineering. 

Therefore, civil and environmental engineers from all walks of life need guidance or knowledge about the principles of engineering drawing (which cuts across whole regions and continents) to make designs that can communicate infrastructural information in a reliable and unambiguous manner.

Since infrastructure projects are commonplace in today’s world across every continent, the principles of engineering drawing are language-independent and have been set up or established in such a way that an engineer who designs an infrastructure in one country can be understood and have their design constructed by an engineer in another or other countries, and vice versa.

Thus, the principles of engineering drawing for infrastructure projects discussed in this post would aid in the clear transmission of information from one person (designer, site engineer, manufacturer, assembler, etc.) to another, regardless of their location in the world.

The principles of engineering drawing are defined and guided by rules embodied in the publications of standards organizations: the UK has its British Standards Institution (BSI); the USA has its American National Standards Institute (ANSI); Germany has its Deutsches Institut fur Normung (DIN), meaning “German Institute for Standardization”. However, the general and probably most important standard organization is the International Standards Organisation (ISO).

General principles that engineering drawings must adhere to

Good enough, all standards organizations have one goal in common: to ensure clear transmission of information from one person to another and in such a way that any engineering design and drawing made in one part of the world can be understood and constructed by other people or engineers in another or other parts of the world, and vice versa.

In regard to infrastructure projects, the Scottish Environment Protection Agency (SEPA) recommends that engineering drawings must be included in permits to control engineering works that are part of large infrastructure projects. Generally, engineering drawings for civil and environmental engineering infrastructure projects must adhere to the following principles:

1. Engineering drawings must utilize a common naming convention that captures the following: drawing name, reference number, date and revision number.

2. Engineering drawings must contain suitably sized texts/specifications to allow for easy reading in print form.

3. Engineering drawings must retain all precise, relevant, or logical information whenever after they have been converted from electronic to print form; for example, all layers of each drawing must be retained and clearly displayed.

4. Engineering drawings must allow a certain degree of flexibility, where appropriate, for all kinds of operators (individuals, designers, site engineers, contractors, agencies, etc.).

5. Engineering drawings must be created to provide a fair, proportionate, and transparent permitting approach platform for all operators.

6. Engineering drawings that are altered beyond their respective limits (i.e., the limit of each individual drawing) must be granted a permit variation “to allow an assessment of the proposed design modifications, and the new drawing to be correctly referenced in the permit”. Examples of design alterations include but may not be limited to:

• extension of a proposed culvert length
• change in gradient of a proposed culvert
• addition of further bank/bed protection
• modification to the length or profile of any proposed realignment
• adjustment or rearrangement of relative overlapping position

Engineering drawing principles for infrastructure projects

The engineering drawings for infrastructure projects referenced in permits must:

1. Only capture the environmental essentials for each activity:

(A) The environmental essentials listed in the figure below are key hydromorphological components that should be considered because of the significant impact they could have on water environments if altered.  

(B) Engineering drawings must not include features that would not protect the water environment or don’t have any hydromorphological bearing; for example: fences and landscape features or structures that aren’t regulated by agencies like SEPA.

2. Be made in such a way that there is due consideration for the water environment and the water environment itself is fully protected.

3. Include a certain or considerable level of agreed design flexibility which should be based on the design opportunities and site-specific constraints (examples of constraints: (i) where the watercourse changes, maybe at a confluence from a tributary to a main watercourse (ii) where there is a significant change in river typology):

(A) It is important to note that at times the final construction works may vary slightly from the initial design and still not cause additional environmental impact. Agencies like SEPA shall assess the degree of flexibility proposed by any applicant and agree or reject an acceptable level of flexibility after considering the complexity of the works and environmental risk.

(B) Any agreed degree of design flexibility (for instance: minimum value, maximum value, range for an environmental essential, etc.) that is eventually agreed upon should be captured within the engineering drawing. For example: (i) minimum channel width of 3.5 – 4.7m (ii) maximum culvert length of 30m.

(C) It is important to note that in some cases it may be possible for the final construction or build location to vary slightly from the initial location.

4. Be easy to understand and ensure that all environmental essentials are clear and clearly understood:

(A) All measurements and key features (for example, culvert length, culvert inlet, culvert outlet, culvert width, etc.) and measurements must be labelled to enable easy identification and reduce the likelihood of being misinterpreted.

(B) There must not be any unnecessary additional detail; for example; cross-referencing of drawing, cross-referencing of other documents, photographs, etc.).

5. Not contain statements and/or notes that indicate a condition, especially as any engineering drawing is a legally binding extension of a permit(s) and thus indicating a condition on it would lead to a loss of transparency and clarity. Example of a condition includes: “All works must be supervised by a trained hydromorphologist”. It is important to note that any conditions aimed at controlling engineering works will be captured within the permit itself.

Introduction to Engineering Drawing (PDF Free Download)

This post contains a link to download a free 231-page PDF eBook titled “Introduction to Engineering Drawing” which consists of detailed information on basic and introductory topics in engineering drawing. The eBook defines/explains concepts in very simple terms and will be extremely useful to beginners or novices who are interested in learning engineering drawing.

The eBook which can be downloaded at the end of the post contains detailed information on the following 11 topics and respective subtopics:

1.      History of Engineering Drawing— Page 5

1.1   Individuals and eras that pioneered and shaped engineering drawing— Page 6

1.2    Through the late 1800s and early 1900s— Page 9

2.      Engineering Drawing Tools & Equipment— Page 14

3.      20 Types of Engineering Drawing Lines and Their Uses— Page 31

4.      Lettering, Dimensioning, and Measurement Systems— Page 45

4.1    Types of Lettering — Page 45

4.2    Dimensioning & 7 types of dimensions — Page 56

4.3    Measurement Systems — Page 67

5.      Symbols, Sections, and Abbreviations— Page 72

5.1    519 Basic Conventional Symbols — Page 72

5.2    How to Use Section Lines & Do Sectioning — Page 92

5.3    Abbreviations — Page 104

6.      Circles, Triangles, Quadrilaterals, and Regular Polygons— Page 114

6.1    How to Draw Circles — Page 114

6.2    How to Draw Triangles — Page 121

6.3    How to Draw Quadrilaterals — Page 129

6.4    How to Draw Regular Polygons — Page 134

7.      Angles and Tangents— Page 145

7.1    How to Construct Angles — Page 145

7.2    How to Draw Tangents — Page 153

8.      Scales and Tolerances— Page 160

8.1    Definition & Types of Scale — Page 160

8.2    Tolerances — Page 168

9.       Freehand Sketching— Page 175

9.1    What is Freehand Sketching? — Page 175

9.2    Importance/Advantages of Freehand Sketching — Page 176

9.3    Freehand Sketching Tools — Page 178

9.4    Freehand Sketching Techniques for Straight Lines and Curved Lines — Page 179

10.    8 Types of Projection & 13 Types of Engineering Drawing— Page 185

10.1   8 Types of Projection — Page 186

10.2   13 Types of Engineering Drawing — Page 200

11.     Basic Engineering Drawing Exercises— Page 219

11.1    How to Draw a Line Between or Through Two Points — Page 220

11.2    How to Draw Parallel Lines — Page 222

11.3    How to Draw Horizontal Lines — Page 224

11.4    How to Draw Vertical Lines — Page 226

11.5    How to Draw Inclined Lines — Page 227

References— Page 231

Download PDF: Introduction to Engineering Drawing

Basic Technical Drawing Exercises (PDF): Angles & Tangents

Download a free PDF copy of “Basic Technical Practice Exercises: Angles & Tangents” at the end of the page. The 14-page eBook contains detailed information on the following topics:

(A) Basic technical drawing exercises for drawing/constructing angles

(i) Procedure for drawing/constructing an angle by using a protractor

(ii) Procedure for drawing/constructing an angle by using a compass and a ruler

(iii) Procedure for drawing/constructing any angle by using CAD (computer-aided design)

(B) Basic technical drawing exercises for drawing/constructing tangents

(i) Procedure for drawing/constructing an arc tangent to a line by using a triangle and a compass

(ii) Procedure for drawing/constructing lines tangent to two circles by using a T-square and triangle or two triangles

(iii) Procedure for drawing/constructing a tangent by using CAD

Download PDF: Basic Technical Drawing Exercises (Angles & Tangents)

Basic Technical Drawing Exercises: Angles & Tangents

This post provides the following basic technical drawing exercises or lessons on how to draw or construct angles and tangents, respectively, using technical drawing tools in different methods:

(A) Basic technical drawing exercises for drawing/constructing angles

(i) Procedure for drawing/constructing an angle by using a protractor

(ii) Procedure for drawing/constructing an angle by using a compass and a ruler

(iii) Procedure for drawing/constructing any angle by using CAD (computer-aided design)

(B) Basic technical drawing exercises for drawing/constructing tangents

(i) Procedure for drawing/constructing an arc tangent to a line by using a triangle and a compass

(ii) Procedure for drawing/constructing lines tangent to two circles by using a T-square and triangle or two triangles

(iii) Procedure for drawing/constructing a tangent by using CAD

How to Draw Circles in Technical & Engineering Drawings

How to Draw Triangles in Technical & Engineering Drawings

(A) Basic technical drawing exercises for drawing/constructing angles

(i) Procedure for drawing/constructing an angle by using a protractor

A protractor can be used to construct various types of angles. Alternatively, angles can be constructed using a compass and ruler, or even CAD (computer-aided drafting), as discussed in the coming sections, respectively.

Take the following steps to construct an angle by using a protractor:

Step 1: Draw a line AB (Figure 1)

Step 2: Position the protractor’s center at the big black point A so that line AB is parallel to and aligned with the line of the protractor

Step 3: Depending on the required angle to be constructed, take A as the origin and mark point C

Step 4: Starting from point A, draw a line to join points A and C to construct the required angle

Figure 1: Steps to construct an angle by using a protractor (Source: Byjus)

(ii) Procedure for drawing/constructing an angle by using a compass and a ruler

The combination of a compass and a ruler is one method that can be used to construct only some particular angles such as 30°, 45°, 60°, 90°, etc. Angles such as 23°, 44°, 57°, etc., can also be constructed by using a compass and ruler.

The construction of 60 degrees (i.e., 60°) angle is one of the most basic and popular constructions which can help in constructing several other angles. Take the following steps to construct 60° by using a compass and ruler:

Step 1: Draw a straight line OB with the left end as point O and the right end as point B (Figure 2).

Step 2: With a compass, draw any desirable radius by placing the compass pointer at O and using the pencil head to construct an arc such that the arc intersects line OB at point P.

Step 3: Place the compass pointer at P and construct an arc such that the arc passes through O and intersects the previous arc at point A.

Step 4: Draw a line originating from O and passing through A.

1

2

3

4 Figure 2: Steps for constructing an angle by using a compass and ruler (Source: Byjus)

Click here to learn how to construct 30°, 45°, 90°, and other angles.

(iii) Procedure for drawing/constructing any angle by using CAD (computer-aided design)

Constructing any angle with CAD/AutoCAD gives more control over the positioning of drawing elements. AutoCAD, specifically, provides Polar Tracking which can be used to constrain the computer cursor into predefined angles. The exact angle direction for any angle is indicated by a long dotted line and the angle. Take the following steps to construct any angle by using CAD:

Step 1: Click the Tools menu, go to Draft Settings, go to the Polar Tracking tab, and put on the Polar Tracking button (Figure 3).

Figure 3: Use of the Polar Tracking command in CAD to construct any angle

Step 2: In the Increment Angle list, select the desired polar tracking angle (Figure 4).

Step 3: To define additional tracking angles, select Additional Angles, click New, and Enter the desired angle into the text box.

Step 4: Go to Polar Angle Measurement, and define any desired polar tracking increments relative to the last created object or based on the UCS.

Step 5: Click OK.

Step 6: On the status bar, right-click the Polar Tracking button, click on any available angle, or go to Settings to define additional tracking angles.

Figure 4: Complete steps for constructing any angle by using CAD

Basic Technical Drawing Exercises (PDF Free Download): Angles & Tangents

How to Draw Quadrilaterals in Technical & Engineering Drawings

How to Draw Regular Polygons in Technical & Engineering Drawings

(B) Basic technical drawing exercises for drawing/constructing tangents

(i) Procedure for drawing/constructing an arc tangent to a line by using a triangle and a compass

Take the following steps to draw an arc tangent to a given line (see Figure 5):

Step 1: Draw line AB and tangent point T and use a triangle to construct a line perpendicular to AB and passing through point T.

Step 2: Define and mark the radius on the perpendicular line to locate the center of the arc. Place the compass’s point at the center of the arc, use the lead/pencil to target the radius of the arc, and draw the arc such that it is tangent to line AB and passes through point T.

Figure 5: Drawing an arc tangent to a line at a given point on the line

(ii) Procedure for drawing/constructing lines tangent to two circles by using a T-square and triangle or two triangles

To draw lines tangent to two circles, do the following:

Step 1: Set the T-square and two triangles or one triangle as shown in Figure 6, then create the tangent lines by placing one side of one of the two triangles between the two circles and projecting a line that is tangent to the circles. Proceed to adjust the other triangle so its vertex passes through the center of one of the two circles, then use a pencil to mark the points of tangency (which are the points where the line is tangent to the two circles, respectively) on the circumference of the two circles, and draw the tangent line. Repeat this step to draw the second tangent line.

Step 2: Draw lines from the centers of the circles perpendicular to the tangent lines and label the tangent points (T₁, T₂, T₃, and T₄) at the points where the lines from the centers of the circles intersect with the tangent lines.

Figure 6: Drawing lines tangent to two circles or arcs by using a T-square and triangle or two triangles

(iii) Procedure for drawing/constructing a tangent by using CAD

Most CAD/AutoCAD systems can automatically locate tangent points. The TAN or TANGENT command is used to draw tangents and can also be used to draw a line such that it is tangent to two curves.  The TAN command generally enables users to draw a line that is tangent to an arc or circle. After selecting the arc or circle for tangency, the “TAN” command should be used via the command line. In AutoCAD, the point of tangency is determined by using the INTERSECTION option to snap the tangent point.

Engineering Drawing Practice Exercises (PDF): Quadrilaterals & Regular Polygons

Download a free PDF copy of “Engineering Drawing Practice Exercises: Quadrilaterals & Regular Polygons” at the end of the page. The 14-page eBook contains detailed information on the following topics:

(A) Engineering drawing practice exercises for drawing/constructing quadrilaterals

(i) Procedure for drawing/constructing a square and any quadrilateral

(ii) Procedure for drawing/constructing any quadrilateral by using CAD (computer-aided design)

(B) Engineering drawing practice exercises for drawing/constructing regular polygons

(i) Procedure for drawing/constructing a pentagon

(ii) Procedure for drawing/constructing an inscribed hexagon

(iii) Procedure for drawing/constructing an inscribed octagon

(iv) Procedure for drawing/constructing any regular polygon

(v) Procedure for drawing/constructing any regular polygon by using CAD

Download PDF: Engineering Drawing Practice Exercises (Quadrilaterals & Regular Polygons)

Engineering Drawing Practice Exercises: Quadrilaterals & Regular Polygons

This post provides the following simple engineering drawing practice exercises or lessons on how to draw or construct quadrilaterals and regular polygons using some engineering drawing tools in different methods:

(A) Engineering drawing practice exercises for drawing/constructing quadrilaterals

(i) Procedure for drawing/constructing a square and any quadrilateral

(ii) Procedure for drawing/constructing any quadrilateral by using CAD (computer-aided design)

(B) Engineering drawing practice exercises for drawing/constructing regular polygons

(i) Procedure for drawing/constructing a pentagon

(ii) Procedure for drawing/constructing an inscribed hexagon

(iii) Procedure for drawing/constructing an inscribed octagon

(iv) Procedure for drawing/constructing any regular polygon

(v) Procedure for drawing/constructing any regular polygon by using CAD

How to Draw Circles in Technical & Engineering Drawings

How to Draw Triangles in Technical & Engineering Drawings

(A) Engineering drawing practice exercises for drawing/constructing quadrilaterals

(i) Procedure for drawing/constructing a square and any quadrilateral

Quadrilaterals can be drawn or constructed using engineering drawing tools & equipment such as T-square, triangle, and protractor to measure equal or unequal angles and create parallel lines. Take the following steps to construct a square or any quadrilateral:

Step 1: Given side AB, use the 45-degree angle of the 45-degree triangle (or use a protractor for any quadrilateral) and place the triangle with the 45-degree angle at A, then draw a line. Repeat the same at B (use a protractor for any angles in any quadrilateral) and the lines would cross to indicate the center of the square (Figure 1).

Step 2: In the case of a square, draw two vertical lines perpendicular to endpoints A and B, respectively, and ensure they intersect the 45-degree construction lines at C and D, respectively. For any quadrilateral, use a protractor and T-square or ruler to create equal or unequal interior angles.

Step 3: To construct a square, draw a line from C to D to get a complete drawing. To construct any quadrilateral, use a T-square or ruler to connect vertices or constructed intersection points of lines.

Figure 1: Steps to draw/construct a square and also any quadrilateral through diagonals

(ii) Procedure for drawing/constructing any quadrilateral by using CAD

Quadrilaterals can be created in CAD by using the POLYGON command, defining the number of sides needed, and deciding whether the sides should be circumscribed or inscribed within a circle. The POLYGON command can be used to draw quadrilaterals and regular polygons of just about any number of sides, with the desired polygon based on the radius of a circumscribed or inscribed circle and the length of an edge of the polygon used to define the size. Figure 2 shows the CAD quick help for the POLYGON (Polygon) command. The RECTANGLE (Rectangle) command is another alternative and quick way to create a square in CAD or AutoCAD.

Figure 2: Drawing a quadrilateral or any polygon by using CAD

Engineering Drawing Practice Exercises (PDF Free Download): Quadrilaterals & Regular Polygons

How to Construct Angles in Technical & Engineering Drawings

How to Draw Tangents in Technical & Engineering Drawings

(B) Engineering drawing practice exercises for drawing/constructing regular polygons

(i) Procedure for drawing/constructing a pentagon

A pentagon has five angles and straight sides and angles that are respectively equal to each other. A pentagon can be drawn or constructed by dividing a circle into five equal parts (i.e., 360 ÷ 5 or 72 degrees each) and using a protractor (or compass and dividers) and scale ruler to locate and mark five equal angles at five vertices, as shown in Figure 3. Any pentagon that is constructed within a circle is called an inscribed pentagon. Take the following steps to construct a pentagon:

Step 1: Draw a circle, divide its circumference into five equal parts (or, divide the circle into five equal parts, originating from the circle’s center at 72 degrees each), and mark five points to represent the vertices of the hexagon.

Step 2: Use a scale ruler, T-square, or any engineering drawing tools & equipment that have a straight edge to join the points or vertices and form or draw the pentagon.

Figure 3: Simple construction of a pentagon by creating and marking five equal distances on a circle’s circumference

(ii) Procedure for drawing/constructing an inscribed hexagon

A hexagon has six equal sides and six equal interior angles at its vertices. A T-square (or straightedge) in combination with a 30/60-degree triangle can be used to construct inscribed or circumscribed within or around a given circle. Alternatively, the circle can be divided into six equal parts (i.e., 360 ÷ 6 or 60 degrees each) and constructed following the previous steps for drawing a pentagon.

An inscribed hexagon is a hexagon or polygon that is drawn with the help of a circle and has all of its five vertices constructed within the circle; a circumscribed hexagon, on the other hand, has five straight edges that are individually outside the circle but tangent to it such that all the vertices are also outside the circle.

When a polygon is inscribed within a circle, the circle is circumscribed around the polygon; when a polygon is circumscribed around a circle, the circle is inscribed within the polygon. 

Take the following steps to construct an inscribed hexagon or a hexagon that is inscribed within a circle:

Step 1: Draw a circle with a center at point A and a horizontal center line BC and mark points B and C where the horizontal center line intersects the circle, as shown in Figure 4.

Step 2: Construct and draw two diagonals such that they pass through center A and are at 60 degrees to the horizontal line BC, then mark the points D, E, F, and G where the diagonals intersect the circle.

Step 3: Use a ruler or T-square to connect the intersection points and draw an inscribed hexagon.

Figure 4: Simple construction of an inscribed hexagon

(iii) Procedure for drawing/constructing an inscribed octagon

An octagon is a polygon that has eight equal straight sides and equal angles; in other words, it is an eight-sided polygon. A circle (360 degrees) can be divided into eight equal parts (i.e., 45 degrees each, originating from the center of the circle) and used to draw an octagon. Take the following steps to construct an inscribed octagon:

Step 1: Draw a circle with a center at point A and a horizontal center line EH and mark points E and H where the horizontal center line intersects the circle; then draw a vertical center line BC and mark points B and C where the center line intersects the circle, as shown in Figure 5.

Step 2: Construct and draw two diagonals such that they pass through center A and are at 45 degrees to either horizontal line EH or vertical line BC, and mark the points D, F, G, and I where the diagonals intersect the circle.

Step 3: Use a ruler or T-square to connect the intersection points and draw an inscribed octagon.

Figure 5: Simple construction of an inscribed octagon

(iv) Procedure for drawing/constructing any regular polygon

Any polygon with n number of straight sides can be drawn by dividing a circle into n equal parts (i.e., the number of sides for the polygon) and using a protractor (or compass and dividers) and scale ruler to locate and mark n number of equal angles or n number of vertices and join them to form the polygon.

Alternatively, any n-sided ­polygon with n number of straight sides can be drawn by dividing the circumference of a circle into n equal parts and using a protractor (or compass and dividers) and scale ruler to complete the job.

(v) Procedure for drawing/constructing any regular polygon by using CAD

Most CAD systems have a POLYGON command that can be used to draw any regular polygon of n (a given number) of sides and sizes or sides of equal length. Generally, the POLYGON command can be used to draw quadrilaterals along with regular polygons of just about any number of sides. Figure 6 shows the CAD quick help for the POLYGON (Polygon) command.

Figure 6: Drawing any polygon by using CAD

Engineering Drawing Exercises for Beginners (PDF): Circles & Triangles

Download a free PDF copy of “Engineering Drawing Exercises for Beginners: Circles & Triangles” at the end of the page. The 13-page eBook contains detailed information on the following topics:

(A) Engineering drawing exercises for drawing/constructing circles

(i) Procedure for drawing/constructing a circle by using a compass

(ii) Procedure for drawing/constructing a circle by using a template

(B) Engineering drawing exercises for drawing/constructing triangles

(i) Procedure for drawing/constructing a triangle, given the lengths of the respective sides and a compass.

(ii) Procedure for drawing/constructing a right-angled triangle, given the hypotenuse and one side.

(iii) Procedure for drawing/constructing an equilateral triangle by using a compass.

(iv) Alternate procedure for drawing/constructing an equilateral triangle by using the 60-degree angle of the 30/60 triangle.

Download PDF: Engineering Drawing Exercises for Beginners (Circles & Triangles)

Engineering Drawing Exercises for Beginners: Circles & Triangles

It takes either talent, practice, or patience—or the combination of two or three out of the three—to master or perfect one’s engineering drawing skill using engineering drawing tools & equipment.

Beginners, novices, or people who are new to the field of engineering drawing may have a tougher time developing their drawing skills and getting used to engineering drawing.

However, with patience, even those who are unskilled can become skilled and produce good drawings if they practice and practice and maybe even practice some more engineering drawing exercises, especially when necessary.

This post provides the following simple engineering drawing exercises or lessons for beginners/novices who are interested learning how to draw or construct circles and triangles using various methods:

(A) Engineering drawing exercises for drawing/constructing circles

(i) Procedure for drawing/constructing a circle by using a compass

(ii) Procedure for drawing/constructing a circle by using a template

(B) Engineering drawing exercises for drawing/constructing triangles

(i) Procedure for drawing/constructing a triangle, given the lengths of the respective sides and a compass.

(ii) Procedure for drawing/constructing a right-angled triangle, given the hypotenuse and one side.

(iii) Procedure for drawing/constructing an equilateral triangle by using a compass.

(iv) Alternate procedure for drawing/constructing an equilateral triangle by using the 60-degree angle of the 30/60 triangle.

How to Draw Quadrilaterals

How to Draw Regular Polygons

(A) Engineering drawing exercises for drawing/constructing circles

(i) Procedure for drawing/constructing a circle by using a compass

The conventional method employed in drawing or constructing a circle in engineering drawing starts with center lines which help to (1) site or set up a location for the centers of circles (2) represent any of the major axes of cylinders, cones, and other curved surfaces, and (3) represent lines of symmetry.

Take the following steps to construct a circle by using a compass:

Step 1: Draw two lines or center lines directly perpendicular to each other in order to locate and mark the center of the circle, and proceed to mark the desired radius on one of the center lines (Figure 1).

Step 2: Place the compass point at the intersection of the center lines and set the compass pencil point to the desired radius.

Step 3: Draw the circle by turning the compass pencil in the clockwise or counter-clockwise direction.

Figure 1: Steps to draw a circle with a compass

Figure 2 shows the multiview drawing for a cylinder. The top view consists of a horizontal center line and a vertical center line intersecting, with the intersection point located and established as the circle’s center. The front view beneath the top view shows a center line which is the location of the cylinder’s axis.

Figure 2: Multiview drawing of a cylinder showing the use of center lines to establish the centers of two different views

(ii) Procedure for drawing/constructing a circle by using a template

A circle template is used to draw circles; in many cases, templates make drawings faster than compasses. Circle template is made of plastic and has circular holes of various diameters, with each circle having a specific diameter.

Take the following steps to draw a circle by using a template:

Step 1: Establish the center of the circle by using center lines (Figure 3).

Step 2: Place/position the circle template to cover the desired radius or diameter. The template can be adjusted for center lines to align with precise marks on/of the template.

Step 3: Use a pencil to draw the circle by tracing it around the boundaries of the selected circle template diameter.

Figure 3: A template and steps involved in drawing a circle

Engineering Drawing Exercises for Beginners (PDF Free Download): Circles & Triangles

How to Draw Tangents

How to Construct Angles

(B) Engineering drawing exercises for drawing/constructing triangles

(i) Procedure for drawing/constructing a triangle, given the lengths of the respective sides and a compass

Take the following steps to construct a triangle by using a compass:

Step 1: Assuming you’ve been given the length of sides A, B, and C respectively without any interior angles, you can start by drawing any one of the sides, for example, A.

Step 2: With the compass pointer placed at one end of A and the pencil set at a desired radius, draw an arc with a radius equal to length B.

Step 3: From the only other end of line A, draw another arc with a radius equal to length C and intersect the arc associated with length B.

Step 4: Draw sides B and C, respectively, by joining one endpoint of line A to the point of intersection of the two arcs and the other endpoint of line A to the same point of intersection of the two arcs constructed as stated in steps 2 and 3 above.

Figure 4: Constructing a triangle, given the lengths of the sides and a compass

(ii) Procedure for drawing/constructing a right-angled triangle, given the hypotenuse and one side

Take the following steps, given the lengths of sides S and R, respectively (Figure 5):

Step 1: Draw AB equal to diameter S and use a compass to draw a semicircle.

Step 2: With A (or one end of AB) as center and R as radius, draw an arc to intersect the semicircle (Step 1) at C.

Step 3: Draw AC (A to C) and BC (B to C) to complete the right-angled triangle.

Figure 5: Constructing a right-angled triangle, given the hypotenuse and one side

(iii) Procedure for drawing/constructing an equilateral triangle by using a compass

Take following steps (Figure 6A):

Step 1: Given the length of side D, extend and set the compass so it is equal in length with D.

Step 2: Place the compass pointer at one end of side D and draw an arc.

Step 3: Place the compass pointer at the other end of side D and draw an arc.

Step 4: Draw a line from one end of side D to the intersection of the two arcs, and another line from the other end of side D to the intersection of the two arcs.

Figure 6A: Constructing an equilateral triangle by using a compass

(iv) Alternate Procedure for drawing/constructing an equilateral triangle by using the 60-degree angle of the 30/60 triangle

Take the following steps (Figure 6B):

Step 1: Place the 30/60 degree triangle so that its 60-degree angle is at the base.

Step 2: Use a pencil to draw the two sides that are not vertical (Alternatively, use a pencil to draw the two sides that are not horizontal).

Step 3: Flip the 30/60 degree triangle so that its 60-degree angle is at the base and other end, and use a pencil to repeat step 2, then proceed to draw the whole equilateral triangle.

Figure 6B: Constructing an equilateral triangle by using the 60-degree angle of the 30/60 triangle

Definition & Importance of Freehand Sketching in Technical/Engineering Drawings

Although drawing tools/equipment or instruments are usually employed in creating basic types of drawings such as computer drawings/models and instrument, technical, and engineering drawings, they can also be used to create freehand sketches as well.

Generally, the objects or structures on technical and engineering drawings, which are graphical representations, can be created via any one of three methods: mechanical drawing, freehand drawing, or computer/digital drawing (i.e., computer-aided design a.k.a. CAD).

Definition of freehand sketching: what is freehand sketching?

Freehand sketching (also known as “technical sketching”) is a procedure that involves the use of one’s hand to draw or create a “brief” or “rough”—and usually preliminary—drawing of a technical or engineering object or structure without the aid of drawing tools/equipment or instruments. 

Typically, freehand sketches are not very well structured; they are also usually less finished or incomplete. Good freehand sketches are not expected to be as good or have straight/uniform edges as drawings produced by traditional instruments or CAD.

Freehand sketching is convenient because it requires the use of only one’s hand, a pencil, an eraser, and paper. The main difference between a drawing produced by traditional instruments or CAD and a drawing produced by freehand sketching can be clearly seen in the quality of lines that represent the drawn object or structure illustrated or expressed by both (i.e.,  traditional instruments or CAD and freehand sketching), respectively.

However, one needs to understand that freehand sketches are not meant to be as accurate or perfect as drawings produced by drawing tools/equipment or instruments; but this is okay, insofar as the freehand sketches represent what needs to be graphically represented or illustrated for technical or non-technical audiences, or any kind of audience it is intended for.

It may be convenient or advisable to always start any technical or engineering design, drawing, or project with some good freehand sketches.

Importance/Advantages of freehand sketching/drawing in technical and engineering drawings

The importance/advantages of freehand sketching are, but may not be limited to:

1. Freehand sketching is a fast form of communication that makes visual communication very easy whenever certain kinds of technical or engineering concepts are being discussed with people at home or at work in a professional environment.

2. Freehand sketching helps to organize one’s thoughts and eliminate or at least minimize errors in final or finished drawings.

3. Freehand sketching helps to quickly produce and easily modify both formal and informal or non-restrictive sketches to communicate both geometric and non-geometric information.

4. Freehand sketching helps to quickly establish layout features and dimensions for later use or transfer to formal drawings.

5. Freehand sketching saves many hours of effort and work before the formal or finished drawing commences.

6. Freehand sketching helps in decision-making on how finished or final drawings should be.

7. Freehand sketching helps in determining adequate sheet layout and the size of final or finished drawings.

8. Freehand sketching helps in keeping records or notes of stages involved in designing from the beginning to the final drawing/design prior to formal drafting.

9. Freehand sketching inspires one to create or capture mental images of ideas and develop them into better and permanent forms, without much difficulty.

Types of Scale in Engineering Drawing (PDF Free Download)

Download a free PDF copy of “Types of Scale in Engineering Drawing” at the end of the page. The 11-page eBook contains information on the following topics and subtopics:

1. Definition of a scale in engineering drawing

2. Types of scale in engineering drawing

3. How scales are specified on engineering drawings

4. Advice when choosing a scale for paper drawing

5. Scale in CAD (computer-aided design)

Download PDF: Types of Scale in Engineering Drawing

Types of Scale in Engineering Drawing

Scales make it possible for drafters and designers to represent large engineering objects or structures on paper or printed drawing, especially when it’s not always possible to represent their full sizes on paper or printed drawing. CAD, on the other hand, can represent objects or structures according to their actual sizes.

The engineering drawing of an object or structure is “scaled” or drawn “to scale” because its actual size is either too big to fit on drawing paper or would be too small to be seen or viewed conveniently if it isn’t scaled up or enlarged on drawing paper.

For instance, for a real-life microchip circuit to be clearly viewed and understood, its full size (which is actually tiny) has to be scaled up or drawn at a size that is thousands of times its actual or real-life size. 

Types of Scale in Engineering Drawing (PDF Free Download)

The scale of any engineering drawing should be clearly indicated in the title block, and any drawing that is scaled at “full size” should be labelled FULL SIZE, implying that the drawing should be scaled at a ratio of 1:1.

Definition of a scale in engineering drawing

In engineering drawing, a “scale” or “drawing scale” is defined as any ratio that expresses or represents the relationship between the actual size of an object and the object’s size on a drawing. It can also be defined as any ratio that expresses the proportional relationship between a drawing and the full/actual size of the object or structure it represents.

It’s only possible to represent one of the floors of a 5-storey building, for instance, on drawing paper if the actual or full size of the storey building is scaled down or reduced to fit on paper.

Conversely, the actual/real size of an object that is very small in real life may not be clearly viewed if its actual size is indicated on drawing paper; therefore, it has to be enlarged, scaled up, or drawn so that the drawing is a number of times larger than its actual/real full size and can be conveniently viewed on paper.

Different scales are often used to represent various kinds of objects on different types of engineering drawing views to enable viewers to visualize objects clearly, regardless of their actual or real-life size. 

If the object represented on an engineering drawing is not scaled, NONE is indicated in the scale area of the drawing paper’s title block. Alternatively, the abbreviation NTS may be used in the form that appears on older types of engineering drawings.

The scale instruments (or engineering drawing scales) used for indicating the dimension(s) of objects are usually six or twelve inches long and made of either plastic, wood, or metal material.

Scale instruments that have linear and triangular (called “triangular scale”) cross-sections, respectively, are commonly used in engineering drawing. Triangular scales have a greater advantage because their combination of several scales indicated separately on each of their three sides.

Figure 1: Part of an engineering drawing scale instrument that has a linear cross-section

Figure 2: Part of an engineering drawing scale instrument that has a triangular cross-section

Types of scale in engineering drawing

The most common types of scale used in engineering drawing include:

 1. Civil engineer’s scale: is the type of engineering drawing scale commonly used to draw complex or large structures and maps.

2. Mechanical engineer’s scale: is the type of engineering drawing scale commonly used to draw mechanical parts.

3. Architect’s or architectural scale: is the type of engineering drawing scale commonly used to draw buildings and structural layouts in civil, building, and structural engineering, respectively.

4. Combination scale: is the type of engineering drawing scale that has a combination of engineering, metric, and architectural components on it—i.e., it has many components on one/a single scale.

How scales are specified on engineering drawings

Although various methods are used to specify or note scales on engineering drawings, all of them express one thing or have one common characteristic: the relationship between the size of the object drawn on paper and the actual size of the object itself in real life.

For example, the scale for an object drawn on paper at half its actual (or real-life) size can be expressed in three different ways in the title block of a drawing paper:

• SCALE: 1:2
• SCALE: 1/­2
• SCALE: 0.5

Unlike a full-size drawing that is labelled as FULL SIZE, a half-size drawing is labelled as HALF SIZE or 1:2. Other smaller or reduced scales such as quarter size (1:4), eighth size (1:8), sixteenth size (1:16), etc., can also be used. Larger or enlarged scales may include 2:1 (double size), 3:1 (triple size), 4:1 (quadruple size), 10:1 (denary size), 100:1 (hundred-fold size), etc.

Generally, speaking, engineering drawing scales are usually written in the following formats:

• 1:1 — Full size
• 1:2 — Half size
• 1:5 — Fifth size
• 1:10 — Tenth size
• 1:20 — Twentieth size
• 1:50 — Fiftieth size

In the common scales listed above, the value on the left (i.e., 1) usually represents the scale factor. The scales or drawing ratios can be reduced or increased by multiplying or dividing them by 10. For example, the twentieth size or scale 1:20 can be reduced to scale 1:200 scale multiplying by 10.

Whenever the value on the left part of a scale is greater than 1, it implies that the drawing that expresses an object is larger than the object’s actual size. A smaller value implies that the drawing that expresses an object is smaller in size than the object’s actual or real-life size.

Figure 3 shows one rectangle drawn at two different scales: the first rectangle is drawn at a scale of 1:1 which represents the rectangle’s actual, full, or true size; the second rectangle is drawn at a scale of 2:1 which represents twice the rectangle’s actual or true size. It’s important to note that in both scales, the dimension of magnitude 3.00 remains the same, regardless of the unit used.

Figure 3: A rectangle drawn to two different scales: 1:1 (i.e., full size) and 2:1 (i.e., double size)

Figure 4 shows the front view of an object drawn at three different scales: the first view is drawn at a scale of 1:1 which represents the actual size of the object; the second view is drawn at a scale of 1:2 which represents half size or half of the object’s actual size; lastly, the third view is drawn at a scale of 2:1 which represents twice the object’s actual size.

Figure 4: The full, reduced, and enlarged scales of an object’s front view

Advice when choosing a scale for paper drawing

Before selecting a particular paper size for the engineering drawing of an object, determine the area or combination of the longest vertical and horizontal dimensions, respectively, of the object to be drawn.

This would give a precise idea about the adequate size of paper needed for the drawing, especially in regard to a particular chosen scale that can enable the drawing of the object to fit on paper.

Scale in CAD (computer-aided design)

Usually, CAD drawings are created in full scale or full size which automatically shows the true dimensions of the object. The desired units of measurement or dimensions have to be set when starting CAD drawings which are scaled to fit any chosen size of the paper to be printed or plotted.

The scale number on a CAD drawing plot represents the plot or printed scale which is not the same as the scale applied when creating the CAD drawing. When creating the scaled plot, appropriate adjustments have to be made on text sizes to ensure that they are not too big or too small.

Tangency in Engineering Drawing

The use and construction of tangents is very essential in designing and drawing engineering objects, parts, or structures. Tangencies or tangent conditions can be constructed by using engineering drawing tools/equipment such as T-square, triangles, and compass. Also, CAD which is a digital engineering drawing tool/equipment, can be used to construct tangents, easily and automatically.

What is a tangent in engineering drawing?

A tangent is a line that passes through, touches, or intersects only one point located on the surface of an arc or on the circumference/surface of a circle. The point where a tangent line intersects a circle is called the “point of tangency”.

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A point of tangency or tangent condition occurs when a straight line intersects a curve at only one point. In other words, a line is tangent if it touches only one point on a surface.

What is tangency in engineering drawing?

Tangency is a condition whereby lines intersect at only one point without crossing each other. For example, a circle and a line are in a state of tangency (i.e., they are tangent to each other) if the circle intersects or touches only one point on the line. It’s also possible for two curves to be tangent to each other in the same way—by touching each other at only one point.

Figure 1: Different tangent conditions or tangency in engineering drawing

Figure 2: Tangent and non-tangent conditions, respectively, in engineering drawing

How to use the combination of a triangle and compass to draw an arc tangent to a line at a given point

Take the following steps to draw an arc tangent to a line using the combination of a triangle and compass (see Figure 3):

(i) Draw line AB and establish or locate tangent point T, then use a triangle to draw a line perpendicular to AB such that it is touching point T.

(ii) Mark the desired radius on the perpendicular line to establish the center of the arc, place the compass’s point at the center of the arc, use the lead/pencil to target the radius of the arc, and draw the arc to be tangent to line AB and touch point T.

Figure 3: Using or applying the combination of a triangle and compass to draw an arc tangent to a line at a given point

How to use a T-square and triangle or two triangles to draw lines tangent to two circles

Take the following steps to draw lines tangent to two circles:

(i) Set the T-square and two triangles or one triangle (Figure 4) and create tangent lines by placing one side of one of the two triangles between the two circles and projecting a line that is tangent to the circles; adjust the other triangle so its vertex passes through the center of one of the two circles, and use a pencil to mark the points of tangency (which are the points where the line is tangent to the two circles, respectively) on the circumference of the two circles, and draw the tangent line. Repeat this step to draw the second tangent line.

(ii) Draw lines from the centers of the circles perpendicular to the tangent lines, and label the tangent points (T₁, T₂, T₃, and T₄) at the points where the lines from the centers of the circles intersect with the tangent lines.

Figure 4: Using a T-square and triangle or two triangles to draw lines tangent to two circles

How use CAD to draw a tangent

Most CAD systems can automatically locate tangent points. The TAN command is used in drawing tangents in AutoCAD; it enables users to draw a line that is tangent to an arc or circle. After selecting the arc or circle for tangency, the “TAN” command should be used via the command line. The TAN or TANGENT command can be used to draw a line that is tangent to two curves. In AutoCAD, the point of tangency is determined by using the INTERSECTION option to snap the tangent point.

Types of Angles in Engineering Drawing

What is an angle?

Different types of angles are widely used in engineering drawing and practice and other fields as well. Without angles, it would be impossible to do many designs and express many objects, graphically.

An angle can be defined as the space between two straight lines or planes that intersect or meet at a point called the “vertex” of the angle”. An angle can also be defined as the magnitude or degree of inclination of one line or plane to another.

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In engineering drawing, angles are measured or expressed in radians or degrees, respectively. A degree consists of 60 minutes (i.e., 60′) and a minute consists of 60 seconds (i.e., 60″). The angle between two lines or planes is often denoted using Greek letters such as θ (theta), α (alpha), β (beta), etc.

Six common types of angles in engineering drawing

Based on magnitude (in degrees), any angle can be classified into one of the following six main types of angles used in engineering drawing:

• Acute angle: An acute angle is any angle that is less than 90 degrees (i.e., 90°) about the vertex.
• Right angle: A right angle is any angle that is exactly 90 degrees about the vertex.
• Obtuse angle: An obtuse angle is any angle that is more than 90 degrees and less than 180 degrees—i.e., any angle between 90° and 180° about the vertex.
• Straight angle: A straight angle is any angle that is exactly 180 degrees about the vertex.
• Reflex angle: A reflex angle is any angle that is between 180 and 360 degrees about the vertex.
• Full rotation or complete circle angle: A full rotation or complete circle angle is any angle that is exactly 360 degrees about the vertex.

Figure: Six common types of angle in engineering drawing

Click here to learn how to construct an angle by using any of the following engineering drawing tools/equipment:

• A protractor
• The combination of a compass and a ruler, and
• CAD

Sectioning in Engineering Drawing (PDF Free Download)

Download a free PDF copy of “Sectioning in Engineering Drawing” at the end of the page. The 16-page eBook contains detailed information on the following topics:

• What is a section and sectioning in engineering drawing?
• Types of section in engineering drawing
• Four steps for visualizing and creating full section views

Download PDF: Sectioning in Engineering Drawing

Engineering Drawing Symbols (PDF Free Download)

Download a free PDF copy of “Engineering Drawing Symbols” at the end of the page. The 23-page eBook contains different kinds of symbols under the following 11 types or categories of engineering drawing symbols:

• Material symbols
• Building symbols
• Piping symbols
• Refrigeration symbols
• Electrical/electronic symbols
• Dimensioning and tolerancing (GDT) symbols
• Links/linkage symbols
• Weld symbols
• External and internal thread symbols
• Rivet symbols
• Topographic map symbols

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Engineering Drawing Symbols

Engineering drawing symbols, which are part of engineering drawing standards, are used to represent basic features, materials, or details of an object on a drawing. Engineering drawing standards have glossaries of different types of symbols that are widely used on engineering drawings.

Engineering Drawing Symbols (PDF Free Download)

This post contains a list of many engineering drawing symbols under the following 11 types or categories of symbols in engineering drawing:

• Material symbols
• Building symbols
• Piping symbols
• Refrigeration symbols
• Electrical/electronic symbols
• Dimensioning and tolerancing (GDT) symbols
• Links/linkage symbols
• Weld symbols
• External and internal thread symbols
• Rivet symbols
• Topographic map symbols

(1) Material symbols

Figure 1 shows common material symbols in engineering drawing:

Figure 1: Material symbols

(2) Building symbols

Figure 2 shows commonly used building symbols in engineering drawing:

Figure 2: Building symbols

(3) Piping symbols

Figure 3 shows common piping symbols in engineering drawing:

Figure 3: Piping symbols

(4) Refrigeration symbols

Figure 4 shows commonly used refrigeration symbols in engineering drawing:

Figure 4:  Refrigeration symbols

(5) Electrical/electronic symbols

Figure 5 shows common electrical/electronic symbols in engineering drawing:

Figure 5: Electrical/electronic symbols

(6) Dimensioning & tolerancing (GDT) symbols

Figure 6 shows commonly used dimensioning & tolerancing (or geometric dimensioning & tolerancing: GDT) symbols in engineering drawing:

Figure 6: Dimensioning & tolerancing symbols

(7) Links/linkage symbols

Figure 7 shows common links/linkage symbols, while Figure 8 shows applications of links/linkage symbols in engineering drawing (Note: The applications are not links/linkage symbols but they consist of links.).:

Figure 7: Links/linkage symbols

Figure 8: Applications of linkage symbols

(8) Weld symbols

Figure 9 shows commonly used weld symbols in engineering drawing:

Figure 9: Weld symbols

(9) External and internal thread symbols

Figure 10 shows a simplified symbol or representation and a schematic symbol (which is an alternative to the simplified one) for external threads in engineering drawing, and Figure 11 shows simplified symbols and their corresponding alternative schematic symbols for internal threads:

Figure 10: External thread symbol: simplified symbol or schematic symbol

Figure 11: Internal thread symbols: simplified symbols or schematic symbols

(10) Rivet symbols

Figure 12 shows commonly used rivet symbols in engineering drawing:

Figure 12: Rivet symbols

(11) Topographic map symbols

Figure 13 shows common topographic map symbols in engineering drawing:

Figure 13: Topographic map symbols

Technical Drawing Instruments/Tools (PDF Free Download)

At the end of this page, download a free PDF eBook that contains information on the following types of technical drawing instruments:

1. Computer-aided design/drafting (CAD)

2. Drawing board

3. Drawing paper/sheet

4. Masking tape (or drafting tape)

5. Drawing set

6. Drawing pencil

7. Sharpener

8. Eraser & erasing shield

9. Dusting brush

10. T-square (or straightedge)

11. Set squares

12. Protractor

13. French curve (or irregular curve)

14. Divider

15. Compass

16. Scales

17. Templates

Download PDF: Technical Drawing Instruments/Tools

Types of Lines in Technical Drawing and Their Uses (PDF Free Download)

The types of lines used in technical drawing are perhaps the most important thing in technical drawing practice, especially because they illustrate how shapes and sizes of objects or objects would appear in real life after they have been constructed.

The types of lines used on technical drawings help viewers communicate, understand, and easily pass over important information. A free PDF copy on the following types of lines in technical drawing and their respective uses can be downloaded at the end of this page:

1. Break line

2. Center line (or, long/short-dashed thin line)

3. Chain line

4. Construction line

5. Continuous thick line

6. Continuous thin line

7. Cutting plane line (viewing plane or section line)

8. Dimension line

9. Extension line

10. Freehand break line (or continuous narrow irregular line)

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11. Hatching line (or section line)

12. Hidden line

13. Leader line

14. Long break line (or continuous thin straight line with zigzags)

15. Match line

16. Miter line (inclined projection line)

17. Phantom line

18. Stitch line

19. Symmetry line

20. Visible line

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Dimensioning in Engineering Drawing (PDF Free Download)

Download a free PDF copy of “Dimensioning in Engineering Drawing” at the end of the page. The 15-page eBook contains information on the following topics and subtopics:

1. Definition of the terms dimensioning and dimensions in engineering drawing

2. Classification of dimension in engineering drawing

3. Units of dimensions/measurements in engineering drawing

4. Seven types of dimension in engineering drawing

• Linear dimension
• Angular dimension
• Diametral dimension
• Radial dimension
• Ordinate (or coordinate) dimension
• Reference dimension
• Note dimension or notes

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Dimensioning in Engineering Drawing

It is essential not only to be able to describe the form, shape, or structure of engineering objects or features, but to also be able to describe their sizes and locations. If you have defined the shape of an object by geometrical description on paper or computer, you would need to use the technique of dimensioning to add size information to engineering objects, parts, or structures in the form of dimensions.

When creating 2D or 3D drawings or models either by hand or computer-aided design/drafting (CAD) systems, you have to strictly adhere to widely or universally accepted standards for dimensioning (or setting dimensions) in engineering drawing in order to get your information across by making it understandable to whomever may come across it.

Selecting particular locations or spots for placement/locating dimensions requires some level of understanding and intelligence that CAD systems may not be able to teach you. Proper placement ensures clarity. Therefore, it’s up to you or any CAD user to understand how to use dimensioning in ways that can carry along every individual who has business with a drawing.

PDF Free Download: Dimensioning in Engineering Drawing

1. Definition of dimensioning and dimensions in engineering drawing: what is dimensioning in engineering drawing?

Dimensioning in engineering drawing is the process of adding data/information about the size of an engineering object, part, feature, or structure to a drawing. Dimensioning can also be defined as the process of inscribing or expressing the geometry (length, area, volume, etc.) or spatial shape and alignment of an object or feature through the use of numbers or numerical values. In other words, dimensioning is the process of indicating dimensions or measurements and their respective magnitudes and directions and the tolerance required for each, on engineering drawings.

A dimension on the other hand is the magnitude or extent of a numerical value (especially length, width, or height) in a particular direction, expressed in appropriate units of measurement to define the size, form, structure, orientation, or location of an object, a feature, or part of something. Dimensions help to describe an object clearly and completely.

Dimensions are expressed through widely recognized standard symbols during dimensioning to provide more details that graphic drawings or representations won’t be able to communicate or provide in entirety on engineering drawings.

2. Classification of dimension in engineering drawing

Each complete detail in engineering drawing usually has multi-views and dimensions that describe the shape and size of the object in the drawing. Dimensions in engineering drawing are of two classifications: size (or functional) dimension and location (or datum) dimension.

Size (or functional) dimensions are used directly on graphic engineering objects or features to express specific sizes, and they can be linked to a part or feature in the form of a note. Location (or datum) dimensions, on the other hand, express the relationship between different features of an object.

3. Units of dimensions/measurements in engineering drawing

The standard units of linear measurement used when dimensioning in engineering drawing and on documents include metric units in millimeters (abbreviated as mm) and the U.S. (United States) customary units in inches (abbreviated as in).

However, the use of either millimeters or inches depends on the intention or needs of the individual. Most countries outside the USA use the metric or international system of units (SI), while the customary system is widely used in the United States because of multinational company affiliations and global trade.

Whenever all dimensions on an engineering drawing are either in millimeters or inches, the general note “UNLESS OTHERWISE SPECIFIED, ALL DIMENSIONS ARE IN MILLIMETERS (or INCHES, as applicable)” would be indicated on such a drawing.

If all dimensions on a drawing are in millimeters, then the term or word METRIC should be at the upper right corner of the drawing. If dimensions are expressed in inches and indicated beside millimeter dimensions on a millimeter-dimensioned drawing, then the abbreviation IN should follow any inch dimension value.

If millimeter dimensions are shown on an inch-dimensioned drawing, then the symbol MM would be used. Occasionally, companies use dual dimensioning which expresses both metric and inch dimensions or measurements on drawings, as indicated in Figure 1.

Figure 1: Dual-dimensioned engineering drawing indicating both millimeter and inch measurements

4. Seven types of dimension in engineering drawing

1. Linear dimension

Linear dimension is the type of engineering drawing dimension that can be expressed as any of the following two distances:

(A) Horizontal: this distance or measurement is made from left to right (or vice versa) relative to the drawing plane (paper or computer), as shown by the width (the horizontal dimension) in Figure 2. Horizontal and vertical distances can be expressed in standard units of linear measurement—mainly in meters, millimeters, inches, and feet.

(B) Vertical: this distance or measurement is made from up to down (or vice versa) relative to the drawing plane (paper or computer), as shown by depth or height (the vertical dimension) in Figure 2.

Figure 2: Dimensions indicating the width and depth (or height) of an object

2. Angular dimension

Angular dimension is the type of engineering drawing dimension that is indicated either in only degrees or a combination of degrees (°), minutes (′), and seconds (″) which are the units of angular dimension. In any situation(s) where only minutes and seconds are specified, a zero (0) is placed before the number of minutes or seconds, as shown on the last diagram in Figure 2—examples of angular units used in angular dimensioning.

Figure 3: Examples of angular dimensions expressed in degrees and a combination of degrees, minutes, and seconds

3. Diametral dimension

Diametral dimension is the type of engineering drawing dimension that expresses the magnitude of the diameter or straight line connecting the center of a circle with two points on its perimeter. Diametral dimension is used on mostly full circles or arcs whose magnitude is more than half of a full circle. The symbol for diameter is the Greek letter phi Ø.

Figure 4: Dimensions showing the diameter and radius of a hole

4. Radial dimension

Radial dimension is the type of engineering drawing dimension that expresses the magnitude of the radius or distance between the center of a circle or arc (that is less than half of a circle) and any point on a circle’s or arc’s perimeter. The symbol for radius is the capital letter R as shown in Figure 4 above.

5. Ordinate (or coordinate) dimension

Ordinate dimension is the type of engineering drawing dimension that is indicated via rectangular coordinates or rectangular coordinate dimensioning in which a datum line or baseline is established for each Cartesian coordinate and every other dimension is positioned with respect to the datum line or baseline.

Figure 5: An object dimensioned by coordinate dimensions, with a baseline or datum surface as starting point

6. Reference dimension

Reference dimension is the type of engineering drawing dimension that provides extra information that is not essential for fabricating or creating a part or feature. Reference dimension is usually enclosed in parentheses [such as (2.00) as shown in Figure 6] on drawings, only providing certain information which cannot be used to fabricate a feature or part.

Figure 6: An object assigned a reference dimension of 2.00

7. Note dimension or notes

Notes are the type of engineering drawing dimension described by written specifications or words, more detailed than numerical values and clearly point out specific information and sizes of a feature or features.

There are two types of notes:

(A) Specific (or local) note: this is the type of engineering drawing dimension that provides information applicable or relevant to specific features and not the whole drawing. Local notes are linked to specific features on drawing views. Three examples of specific notes include:

Figure 7: Three examples of specific notes

(B) General note: this is the type of engineering drawing note that provides information that is applicable or relevant to the whole drawing. General notes are linked to all drawing views of a drawing. Three examples of general notes include:

(a) FINISH ALL OVER (FAO)

(b) ALL DRAFT ANGLES 3° UNLESS OTHERWISE SPECIFIED

(c) DIMENSIONS APPLY AFTER PLATING

Lettering in Engineering Drawing

The texts that appear on engineering drawings are used to communicate non-graphic information and may be as highly important as graphic information. Without text and lettering, it would be almost impossible to describe engineering drawings completely.

The fact that lettering or lettered text must always be used to completely express and describe the details of an object goes to show just how essential it is for all types of engineering drawing.

Definition of lettering in engineering drawing

Lettering is the act or process of creating, inscribing, or writing letters, titles, subtitles, numbers, notes, fractions, decimal points, symbols, dimension values, equations, and other important non-graphic information to express or illustrate details of engineering objects, parts, features, or structures on drawing paper or CAD. Lettering describes and provides detailed information about each particular drawing: instructions, the size, dimensions, notes, etc.

Lettering can also be defined as any writing process that expresses the details of engineering objects, parts, features, or structures on drawing paper by the use of lettered texts in the form of alphabets, numbers, fractions, and/or decimal points which could also provide detailed specifications for objects.

Common types of lettering in engineering drawing

There are two broad or common classes of lettering in engineering drawing: traditional and computer-aided design/drafting (CADD) lettering; implying that lettering can be done by hand or computer.

The traditional or hand lettering employed in engineering drawing is of two types: free hand lettering and mechanical lettering; while CADD on the other hand could in reality consist of more than the 12 lettering types listed in this post, with images.

1. Traditional lettering

(i) Free hand lettering

Drawing and lettering all started with the hand before evolving into the widely used CADD lettering of today. Although free hand lettering is used much less nowadays, it is still important to master how to write clear, legible, and comprehensible hand-lettered words, numbers, and decimal points that conform to universally accepted or standard styles.

Lettering in engineering drawing can be done with the hand by using “guide lines” which are very light or thin construction lines that serve as guides to create clear and uniform letters. Hard pencils, such as 4H, 5H, or 6H, are often used to construct guide lines from a lettering guide, as shown in Figure 1.

Figure 1: Adjustable lettering guide for creating guidelines and applying hand lettering in engineering drawing

Lettering guides help to conveniently set out text dimensions and inclinations or orientations on engineering drawings; it can be used to create vertical, horizontal, or inclined guidelines. The individual letters are drawn within the guidelines.

Each letter is constructed via a particular style. Figure 2 shows examples of different capital or uppercase letters and numbers in vertical format, while Figure 3 shows examples of different lowercase letters in vertical format.

Figure 2: Capital or uppercase letters and numbers in vertical format

Figure 3: Lowercase letters in vertical format

(ii) Mechanical lettering

All text in traditional drawings was hand lettered and very personalized until Johann Gutenberg invented printing in the 15th century; but with the invention of printing, the text styles used for lettering in engineering drawing became more standardized.

Mechanical lettering guides—such as the lettering template shown in Figure 4, the press-on type, and the lettering machine—were all developed in the years that preceded CADD.

Figure 4: Mechanical lettering guide or template for traditional or hand lettering in engineering drawing

2. Computer-aided design/drafting (CADD) lettering

Computer-aided design/drafting has provided users with many text style options and almost eliminated any need for hand lettering in engineering drawing. One of the greatest advantages that CADD lettering and tools have over traditional lettering and tools is their remarkable speed and also the speed with which text lettering can be done on engineering drawings.

CADD text is grouped and classified according to different characteristics. The style and size of a CADD text type define its font, but the text can vary if bold or italic versions are applied during lettering on engineering drawings. Figure 5 shows the characteristics of a CADD text type. It is important to note that the type size of CADD texts is measured in “points” and each vertical inch consists of 72 points; therefore, a 36-point type CADD text is about ½ inch high.

Figure 5: Important terms associated with each available CADD text or interface

Three major classes of CADD lettering: (A) Alphabets/letters, (B) Numbers and fractions, and (C) Decimal

(A) Lettering of alphabets/letters: 12 types

(i) Sans serif lettering

A Sans serif typeface is a typeface that does not have any serifs, spurs, or sharply pointed projection. For example, the old school and popular Gothic typeface is a sans serif letter or typeface. The Sans serif letters used in engineering drawing are also referred to as Gothic text.

Figure 6: Sans serif lettering using CADD

(ii) Serif lettering

A serif is a spur, small finishing stroke, sharply pointed projection) that is at right angles to the main character stroke of the CADD typeface.

Figure 7: Serif lettering using CADD

(iii) Roman lettering

Figure 8: Roman lettering using CADD

(iv) Italic letters/lettering

Figure 9: Italic letters/lettering using CADD

(v, vi, vii, viii, ix, x, xi, and xii) Seven other different lettering using CADD: AutoCAD Txt Font, Roman Simplex, Roman Duplex, Baskerville, Times New Roman, Playbill, Arial, and Letter Gothic:

Figure 10: Seven other different lettering types using CADD

(B) Lettering of numbers and fractions

When indicating a fraction on engineering drawings, the number in the fraction should be the same size as any other number on the drawing. The height of a fraction should be twice the height of its corresponding whole numbers, and both the numerator and denominator should be about three-fourths as high as the whole number so there can be sufficient space between both of them and the fraction bar which can also be placed diagonally, depending on company or school standards.

Figure 11: Lettering of fractions using CADD

Figure 12: Lettering options for fractions using CADD

(C) Lettering of decimal points

When lettering any dimension value that has a decimal point, the decimal point should be uniform, dense, and large enough for viewers to see, and it should be placed in line with the bottom edge of the text.

Whenever any metric or millimeter dimension is less than 1, a zero should be placed before the decimal point; for example, 0.5. But, whenever an inch dimension is less than 1, a zero should not be placed before the decimal point; for example, .02.

Whenever a metric dimension consists of only whole numbers, neither a decimal point nor a zero should be indicated; for example 24, instead of 24.0.

 

Figure 13: Lettering options for decimal points using CADD

Engineering Drawing Tools (PDF Free Download)

It is important to know the different types of engineering drawing tools usually employed in creating graphic representations or drawings of the shapes and sizes of engineering objects, parts, or features, or structures.

At the end of the page you can download a free PDF copy that contains information on the following types of engineering drawing tools:

1. Computer-aided design/drafting (CAD)

2. Drawing board

3. Drawing paper/sheet

4. Masking tape (or drafting tape)

5. Drawing set

6. Drawing pencil

7. Sharpener

8. Eraser & erasing shield

9. Dusting brush

10. T-square (or straightedge)

11. Set squares

12. Protractor

13. French curve (or irregular curve)

14. Divider

15. Compass

16. Scales

17. Templates

Download PDF: Engineering Drawing Tools

Engineering Drawing Tools & Equipment

Various tools and equipment are often used to produce engineering drawings that are concise, accurate, and clear. Therefore, it’s important to be familiar with all engineering drawing tools and equipment and understand their respective uses.

Generally, engineering drawing tools and equipment or instruments are used to produce three basic types of drawings: freehand drawings/sketches, instrument drawings, and computer drawings/models.

Figure 1: A drawing board and different types of engineering drawing tools

Computer-aided design/drafting (CAD) tool/software plus 16 other traditional drawing tools constitute 17 different engineering drawing tools, viz (NOTE: A free PDF copy of the engineering drawing tools and equipment discussed in this post can be downloaded here.):

1. Computer-aided design/drafting (CAD)

Most modern-day models in engineering drawings are created via computer-aided design/drafting (CAD) systems which are computer software and related computer hardware that evolved from traditional engineering drawing tools such as pencils, T-squares, scales, triangles, protractors, compasses, dividers, etc.

CAD generally employs the same concepts and drafting standards applicable to drawings created by hand via traditional tools, and can be used to produce virtually any type of engineering drawing via programmed commands for circles, lines, triangles, etc. The main benefits of using CAD include:

• Speed
• Accuracy
• The opportunity to demonstrate visual and spacial information in various effective ways.
• The opportunity to quickly demonstrate different types of lines used in engineering drawing.

Figure 2: An engineering drawing from CAD

2. Drawing board

Drawing board is usually made of white pine which, according to WordWeb Dictionary, is a “straight-grained durable and often resinous white to yellowish timber of any of numerous trees of the genus Pinus”. But drawing boards can sometimes be produced from other types of softwood.

Regardless of the type of wood used (typically, soft white pine or basswood), the working or drawing surface of any drawing board should be smooth, flat, and unshakeable, and its working edge must be straight to facilitate the creation of clear drawings.

Figure 3: Different types of drawing board

Figure 4: Drawing board with drawing sheet/paper

3. Drawing paper/sheet

Drawing paper is a material on which engineering drawings are created; it is an engineering drawing tool used to convey graphic information that follows universally accepted standards widely used in practice and many fields. Depending on application, there are different types of drawing paper:

(a) White plain paper, which is manufactured according to International Organization for Standardization (ISO) standard for various paper sizes. Standard drawing sheet sizes are in three series, designated A_n, B_n, and C_n, where subscript n varies according to the paper/sheet size. The variety of “A” plain paper is very common: A₀, A₁, A₂, A₃, and the popular A₄

(b) Profile, plane/profile, and cross-section papers

(c) Tracing paper

Figure 5: Paper/sheet sizes

4. Masking tape (or drafting tape)

Masking tape is used to bind drawing paper with or attach drawing paper to drawing board in order to help prevent unnecessary errors due to misalignment.

Figure 6: Masking tape

5. Drawing set

A drawing set usually consists of a divider/set of dividers, two bow compasses (i.e., a big and a small bow compass), inking points, a tube with extra parts, and a beam compass or a fastening for large arcs and circles.

Figure 7: A drawing set

6. Drawing pencil

The two main types of pencils used in engineering drawing are wooden pencils and mechanical pencils. Wooden pencils are of different grades of hardness. The grades of wooden pencils, designated by a number in conjunction with a letter, are:

• Hard: 9H, 8H, 7H, 6H, 5H, and 4H
• Medium: 3H, 2H, H, F, HB, and B
• Soft: 2B, 3B, 4B, 5B, 6B, and 7B

Generally, B grades of pencils are soft and used for freehand sketching, while H grades are hard and used for instrumental drawings. On the other hand, mechanical pencils (of different lead grades that do not need to be sharpened) can be any of the following sizes: 0.3, 0.5, 0.7, and 0.9 diameters.

Figure 8: Drawing pencils: wooden and mechanical

7. Sharpener

Sharpener is an engineering drawing tool used to sharpen pencils, especially any of the different types of wooden pencils. They can be operated by an electric motor or manually by hand. It may be essential to note that special sharpeners may be required for some pencils or lead holders on pencils.

Figure 9: Sharpener

8. Eraser & erasing shield

Mistakes are part of life—and part of engineering drawing practice too. Erasers are used to delete or erase unnecessary parts of a drawing and make modifications and corrections when necessary. An erasing shield makes the drawing neater by focusing the eraser only on the area that needs to be erased.

Figure 10: Eraser and erasing shield

9. Dusting brush

To keep drawings neat, a dusting brush should be used to gently remove any particles that remain after something has been erased. Eraser or hands should never be used to scrub drawings because they can take the life out of lines and make drawings to be untidy.

Figure 11: Dusting brush

10. T-square (or straightedge)

A T-square (or straightedge) is a parallel edge or engineering drawing tool used to draw horizontal lines and guide triangles in order to create vertical and inclined lines.

The uppermost part or edge of a T-square and the inner edge of the T-square’s head are known as “working edges”. Working edges should be straight and at right angles to each other.

Figure 12: T-square

11. Set squares

Triangles are sometimes regarded as or called set squares which are right-angled triangular plates used to draw and incline lines at 90°, 45°, 60°, or 30° to any of the 3 major axes (x, y, and z). The two main set squares are the 30-60° and 45° triangles, respectively.

Figure 13: Set squares

12. Protractor

Protractor is a semi-circular engineering drawing tool or device which has a center where the starting point of a line can be indicated; it is used for setting off or measuring angles that are different from the common ones found on triangles.

 

Figure 14: Protractor

13. French curve (or irregular curve)

French curves are used to draw curves that are not arcs or circles; examples include parabolas, ellipses, hyperbolas, and involutes. French curves can be used in conjunction with points to draw short elliptical radius curves or mechanical curves with shapes that are not circles or circular arcs. There are many different sizes and forms of French curves.

Figure 15: French curve

14. Divider

Divider is part of drawing set and also worthy of discussion. A divider is an engineering drawing equipment used to divide distances into equal parts or ensure that distances are equally divided.

Figure 16: Divider

15. Compass

Compass is used to draw circles and arcs. Depending on the aim of drawing, it is generally of two types: bow compass and beam compass as shown in Figure 17 a) and b) respectively.

Figure 17: Bow compass and beam compass

16. Scales

Scales are used to measure and establish the lengths of lines or distances. Generally, they are 6 or 12 inches long and made of plastic, wood, or metal. Triangular plastic scales are quite common and provide users with a combination of several scales on each side.

The mechanical engineer’s scale, the civil engineer’s scale, the architectural scale, and especially the metric scale are the most common types of scales used in engineering drawing. There is even a “combination scale” which is the type of scale that has metric, engineering, and architectural components. Figure 18 shows part of a full scale (A) and part of a 1:20 scale (B).

Figure 18: Scales

17. Templates

Templates are an engineering drawing tool used to draw repetitious features including (but may not be limited to) architectural symbols, ellipses, circles, and threaded fasteners.

There are different types of templates: the circle template is used to draw arcs, rounds, circles, and fillets and makes some aspects of drawing much faster than when using a compass; the ellipse template is used to create ellipses. Templates are also of other common shapes, and CAD can create templates of almost anything.

Figure 19: Templates

What is Engineering Drawing? (Free PDF Download Available)

Understanding what engineering drawing is and is not can enhance your creativity in engineering drawing and technical drawing as well. This post provides a detailed explanation that can help you understand what engineering drawing is—and also what it is not or not about: it provides broad definitions of engineering drawing and lists important qualities of a “true engineering drawing”, instead of an artistic one or otherwise. At the end of the post you can download a free PDF copy of this post’s content.

Definitions of engineering drawing: what is engineering drawing?

1. Engineering drawing is a detailed and accurate visual representation of one or more perspectives of an engineering object, structure, shape, idea, or concept through the universal language (i.e., engineering drawing language with instruments or freehand) that employs graphical symbols, scales, page layouts, perspectives, specific dimensions (or units of measurement), visual styles, notation systems, and other components of the codes of practice to illustrate how the engineering object, structure, shape, idea, or concept works or can be constructed. Like the next definition, this one clearly indicates one main thing: the main foundation of any complete engineering drawing is the codes of practice employed in engineering drawings.

Brief History of Engineering Drawing

The Importance of Engineering Drawing

2. Engineering drawing can also be defined as any elaborated and precise handmade or CAD-made 2D and/or 3D graphic presentation of an engineering idea or object that is founded on or produced from the application of projections/perspectives, units of measurement, graphical symbols, scales, and other distinct features that abide by components of the codes of practice employed in the general construction of engineering drawings.

What qualifies a drawing as an engineering drawing: what is engineering about a drawing?

The following qualities automatically qualify a drawing as an engineering drawing: they are also the characteristics or qualities of the 13 different types of engineering drawing:

1. Engineering drawings strictly adhere to general codes of practice, conventions, or regulations—what I call “agreements”—that have adopted the most appropriate and well-structured presentational techniques that conform to specific standards to ensure clarity and prevent information from being misinterpreted. Engineering drawings can be easily distinguished from artistic/visual art drawings due to their distinguished features, notations, title blocks, symbols, different types of lines, and line thicknesses which all strictly adhere to universal codes of practice. Strict adherence to general codes of practice makes it possible for blueprints of various types of engineering drawings to be easily interpreted by different people across the world and quickly developed to completion. 

2. Engineering drawings are precise or accurate, owing to the fact that the objects conveyed on them are represented in actual proportions that can be easily interpreted by the learned (and, to some extent, unlearned) in only one way—only one way—thus keeping preciseness or accuracy intact and carrying everyone along during actual construction. The quality of preciseness or accuracy distinguishes engineering drawings from artistic drawings.

3. Engineering drawing is largely or almost completely multiview—or “more than only one view” in most or all cases (It’s rare or impossible to see a single-view drawing, except maybe for illustration purposes.): the projection of each object is usually displayed from different viewpoints which must all correspond to any adopted scale. 

4. Unlike artistic and abstract drawings which are mainly understood by only their respective creators, engineering drawings are mainly understood by the majority—by everybody who understands the engineering drawing language. This quality enables easy and clear-cut communication between people of different fields, backgrounds, or specialties (architects, designers, engineers, scientists, etc.) clearly distinguishes engineering drawings from artistic drawings.

Free PDF Download: What is Engineering Drawing?

Types of 3D Models Used in Engineering Drawings & Designs

At the time of writing, the three main types of 3D models or modelling methods usually integrated into computer-aided design (CAD) systems for a single software package include: wireframe models/modelling, surface models/modelling, and solid models/modelling. Each of the three has its own strength and weakness.

Although other different types of 3D models are available in CAD systems for engineering drawings/graphics and designs, most of them exist as a subset of the three main types of 3D models and are often used individually for specific purposes.

1. Wireframe model

The Wireframe model/modelling was the first 3D modelling method to be established. It is the type of 3D model that is often used as a starting point in 3D modelling, since they are used in creating a “frame” for each 3D structure.

A wireframe is a three-dimensional model that includes only lines and vertices; it doesn’t contain surfaces, textures, or lighting like a 3D mesh. Rather, a wireframe model comprises only “wires” that represent three-dimensional shapes.

Generally, “wireframe model/modeling” refers to any computer screen display of a model concerning only the edges and contours of the object or artefact it represents.

Wireframes provide the most basic representation of a three-dimensional object or feature. Using simple lines and curves, a wireframe model can represent the “skeleton” for building or any 3D object.

Wireframe models express the outlook of edges and contours of objects via lines, arcs, and circles that are orientated in 3D modelling. The portrayal of contours and edges in the wireframe model was developed from 2D modelling practices.

The wireframe modelling method derived its name from the mental or visual process involved in representing objects, sculptures, or carvings by the use of wires as shown in Figures 1, 2, and 3.

Figure 1: The Wireframe model (lines, arcs, and curves in 3D) of an artefact (Source: Quora)

Figure 2: The Wireframe model of a car (Source: DepositPhotos)

Figure 3: The Wireframe model of the world (Source: PngEgg)

A wireframe model can be created in the same way a 2D CAD drawing is created. Simple geometric tools (such as lines, arcs, and circles) are drawn in 3D to illustrate the orientation of each edge where some surfaces of an object intersect.

Wireframe models don’t look as realistic or “close to reality” as some other models because they incorporate surfaces or boundaries that are often shaded.

A wireframe model can enhance the visualization of 3D equipment which is more difficult to visualize when represented or expressed in 2D. In many cases, it may be important to utilize wireframe modelling during any engineering design.

The main advantage of wireframe 3D models is that they provide a single and clear understanding of shapes and make it possible for objects not to be expressed or represented unambiguously, especially on multi-view drawings.

2. Surface model

Computer-aided design surface modeling/models can be used to specify limits and define an artefact or object based on the stored information regarding its surface.

However, surface models do not assign any material thickness to surfaces, and the outer surfaces of objects (balls, boxes, cubes, etc.) can be shaded between or around the limits specified and defined by the surface models.

Generally, surface models focus on modelling the outer/outside parts of objects, artefacts, shapes, or products, instead of the inner and mechanical parts within.

Figure 4: Surface modeling for Audi car (Source: GrabCAD)

The information or definitions concerning an artefact is stored in the CAD database. This information represents the outer or external boundaries of surfaces that can be part of the 3D model. (The process of storing the definitions of surfaces in the database is called “boundary representation” [BREP].)

To create a surface model, an entire surface doesn’t need to be created at once: only pieces or “patches” need to be combined into a continuous model. In summary, surfaces can be created from bits or pieces that are technically called “patches”.

Each patch can be approximated or interpolated like a spline curve. A patch can be regarded as a “coon’s patch” which is an interpolated surface defined by four boundary curves which consist of points that can be interpolated using mathematical methods.

The surface models employed in computer-aided manufacturing (CAM) need to operate at a high level of accuracy to produce really good and smooth surfaces that may require fewer control points to make their curves more fluid.

3. Solid model

The term “solid models or modelling” is a 3D modelling technique used by solid modellers or designers to create a representation (called a solid) of a solid object. Unlike surface and wireframe models, solid models ensure that objects are geometrically correct and all surfaces meet precisely. 

Solid models not only represent the edges, vertices, and surfaces of the part, they also help determine the locations of points in the space within an object or outside it.

When dealing with the volume occupied by an object of artefact, solid models go way beyond surface models: they store information about the vertex and edge of the 3D wireframe modeller, the surface modeller’s surface definitions, and the volume as well.

Because many solid modellers store the operations used to produce features, it is possible to quickly edit features of objects and easily test, define, and refine the designs that solid models represent.

Figure 5: Three engineering drawing projections and their corresponding solid (shaded) model (Source: ResearchGate)

Solid models are easy to understand, highly accurate, and visually appealing if modelled accurately. Some 3D solid models are often more capable of replacing physical models.

However, 3D solid models work better with analysis packages, as they contain all the information concerning the volumes of objects which are very important in many calculations.

During the refinement process of designs, solid models can be used as a foundation from which centroid, mass properties, moments of inertia, and weight can be estimated as many times as needed.

Figure 6: Difference between Wireframe model and Solid Model (Source: LearnMech)

The behavior of an object or its system can be simulated from the information stored in the solid model which can further provide useful information that may be required for other analyses.

Because solid models define entire objects, their information can be used by finite element analysis (FEA) softwares to automatically generate FEA meshes and break up complex objects into smaller objects, thereby making it even easier to calculate material properties such strain, stress, and heat transfer.

Some solid modelling softwares and FEA are structured to provide this and similar types of analysis. Other modeling softwares even permit direct model optimization based on results from FEA, and they could be used to produce a new version of the model which the modeller can review further.

Types of Models Used in Engineering Drawings & Designs

A model represents or hypothetically describes a complex process, entity, system, device, or theory that helps to predict the model’s behavior. A model can be defined as a small-scale object that is usually built to scale to represent the details of a much larger object.

Models used in engineering drawings, designs, and preliminary works are known as “engineering models” which can be used to hone, perfect, or test any “final” engineering object/product after understanding how it behaves; for example, a test model can be created for a solar-powered vehicle.

This article discusses the following four main types of models used in engineering drawings and designs:

• Descriptive models
• Analytical models
• Two-dimensional (2D) models
• Three-dimensional (3D) models

1. Descriptive models

Descriptive model is the type of model used in engineering drawings and designs to represent an object, system, entity, device, or process in words or in pictures.

Any engineering model that is descriptive is usually expressed as a group of written specifications for a design, an object, a system, an entity, a device, or a process.

The main aim of any descriptive model is to describe and provide enough details to express the image of the final design, object, system, entity, device, process, or product.

In certain situations, descriptive models use representations that are simplified, common, similar or equivalent to something that is well known or can be easily understood.

If all specifications in a descriptive model adhere to the final design, object, system, entity, device, process or product, then it will perform as correctly as expected.

Sketching is one type of descriptive model that can be used to express design ideas on paper. Two-dimensional (2D) and 3D (three-dimensional) computer-aided design (CAD) drawings are also descriptive models.

Although, in certain cases, a physical model or prototype is created to be smaller in scale, it is still regarded as another type of descriptive model.

2. Analytical models

Analytical model is the type of model used in engineering drawings and designs to mathematically or diagrammatically (schematically) represent and predict the future behavior of an object, system, entity, device, process, or product.

For example, an electrical circuit model or simple circuit design model can help to simulate or reproduce the behavior of an actual electrical circuit, or understand how it would function; therefore, an electrical circuit model is an example of an analytical model.

An effective analytical model helps to determine the best aspects of a system’s, an object’s, an entity’s, a device’s, a process’, or a product’s behavior that is important enough to be modelled.

A finite element analysis (FEA) model (like the one employed in calculating essential properties—such as temperature, stresses, etc.—during design of a real object, entity, product, system, device, or process) helps to modify CAD models in a similar way.

A FEA model is a type of model that breaks down models into smaller elements and reduces complicated or complex systems into a series of smaller systems that can assist in problem-solving or understanding and estimating certain properties much more easily.

One requires a certain level of understanding to be able to apply an analytical model: one must be able to distinguish between the model and the actual system, entity, device, process, or product in order to correctly interpret any results.

3. Two-dimensional (2D) models

Traditional paper drawings

Two-dimensional (2D) sketches and multi-view paper drawings are another type of model used in engineering drawings to represent designs in engineering practice.

All information that defines an object can be shown on paper drawing through sketch details that may be represented through many orthographic views and could take a long or longer time to create than CAD drawings.

Because more time and effort are required to modify paper drawings, the labor costs needed to produce them usually outbalance any equipment savings. Another disadvantage of paper drawings is that they are not always accurate or highly accurate.

2D CAD Models

Two-dimensional (2D) CAD models are another type of model used in engineering drawings and designs; although they share the visual characteristics of paper drawings, their accuracy is higher than paper drawings and they can be easily modified.

CAD models represent the full size of objects, unlike paper drawings which usually don’t. Also, in CAD models the user can “snap” to exact locations on objects to be able to determine or define desired sizes and distances.

CAD systems consist of standard symbols that are easy to add and modify; furthermore, they consist of many editing tools that enable users to quickly edit and reuse drawing geometry.

Two-dimensional 2D CAD drawings can be easily and quickly printed to any desired scale and information concerning its characteristics or properties can be singled onto several layers, thus giving the model an advantage and making it more flexible than paper drawing.

Computer-aided design accurately defines the positions of arcs, lines, and other geometry. Whenever the AutoCAD database is queried, it returns information accurately in the exact form it was originally created.

2D constraint-based modelling

Two-dimensional constraint-based modelling is a type of model or modelling technique that was originally started to create 3D models. Constraint-based 2D models provide users with technical aspects that help to define 2D shapes based on their individual geometry.

Users can add relationships like concentricity and tangency between objects/entities in a drawing, and once a concentric or tangential constraint is added between any two shapes or drawings (for e.g., between squares or circles), they will be constrained to remain concentric or tangential and users will be notified whenever they try to make a change that violates a selected geometric constraint.

The dimensions used in engineering drawings constrain the sizes of each drawing’s features, and the relationships defined between components of 2D models are retained by the software used to make changes on the drawings.

Geometric constraints are highly valuable tools used in engineering drawings; however, they must be applied with a proper understanding of basic drawing geometry in order to derive any benefit from them.

Examples of constraints in AutoCAD 2016

The following are the constraints that define 2D objects’ respective geometry in AutoCAD which is widely applied in engineering models and practice:

• “Horizontal”: This constrains lines or pairs of points on objects to remain parallel to only the x-axis
• “Vertical”: This constrains lines or pairs of points on objects to remain parallel to only the y-axis
• “Perpendicular”: This constrains two selected lines to be at an angle of 90° to each other
• “Parallel”: This constrains two selected lines to remain parallel to each other
• “Smooth”: This constrains a spline to be contiguous and maintain G2 or curvature continuity with another entity
• “Tangent”: This constrains two curves to be tangent to each other or to their extensions
• “Coincident”: This constrains two points to stay connected to each other
• “Concentric”: This constrains two arcs, circles, or ellipses to retain or maintain the same center point
• “Collinear”: This constrains two or more line segments to remain along the same line
• “Symmetric”: This constrains two selected objects to remain symmetrical about a specified line
• “Equal”: This constrains selected entities to retain or maintain the same size
• “Fix”: This constrains points, curve points, or line endpoints to stay in fixed position on the coordinate system
• “Linear”: This constrains the distance between two points along the x- or y-axis to be retained
• “Angular”: This constrains the angle between two lines to be retained
• “Aligned”: This constrains a distance between two points to be retained
• “Radius”: This constrains the radius for the curve to be retained
• “Diameter”: This constrains the diameter of the circle to be retained

4. Three-dimensional (3D) models

One must be able to properly interpret 2D models in order to correctly visualize 3D objects. Three-dimensional models are the type of model used in engineering drawings to express design ideas to people who are not familiar with orthographic projection; in addition, 3D models are used to evaluate properties of drawings and designs that are undefined in 2D representations.

Physical models

Physical models serve as a visual reference and are also known as “prototypes” whenever they are created in “full-size” or used to validate final designs.

Physical models are good visual representations of designs; however, if they are not created from materials that would be used in design, their weight and other features won’t match the final product.

Physical prototypes make it possible for designers and people to interact with physical models and understand how designs would eventually look like and function in real life; in addition, they help to uncover and correct many engineering and design problems.

In some cases, depending on the size of an engineering project, a physical model is created to be smaller in scale than the final design. However, physical prototypes lack flexibility and once they’ve been created, it can be difficult, expensive, and time-wasting to modify them. Therefore, it’s advisable to use full-sized physical prototypes late in design processes when major design changes are less likely to be made.

3D CAD models

Three-dimensional CAD models are the type of model that combines the characteristics of descriptive models and analytical models and provides the benefits of both 2D models and physical (prototype) models which were earlier discussed.

The 3D CAD models used in engineering drawing can help generate standard 2D multiview drawings (including rendered and shaded views) for visual representation.

Because 3D CAD models help to accurately depict the geometry of objects or features, they can be used to completely describe the shape, size, and appearance of objects or devices in the same way as any physical or scaled model would.

Virtual reality

Virtual reality (also called “VR”) refers to the process of interacting with a 3D CAD model as if it were real. In virtual reality, the model simulates how a user would interact with a real object, device, or system.

The term “virtual prototype” refers to 3D CAD systems used to represent objects that have at least enough information that can enable people, manufacturers, or designers to acquire the same understanding or information they would acquire from creating, studying, and interacting with a physical model or prototype.

When a virtual reality display is used, users are able to immerse themselves in the model and move about or through it and view it from several viewpoints.

If the conditions of a virtual object are altered, the VR would react in a certain way and provide feedback, or the sensation of its reaction would be provided to the user or person immersed in the virtual reality they subjected themselves to.

Engineering Measurement Units for Length

Engineering drawings are graphic representations of objects, parts, or structures that would eventually be produced, manufactured, or constructed in real life. The dimensions (length, breadth/width, height) and sizes of objects are expressed by engineering measurement units, depending on the units of a particular measurement system; two popular measurement systems include the “Metric System” and the “United State Customary Units” which we will get to in a moment.

Engineering measurement units are fundamental to construction, sciences, architecture, engineering, and many other technical fields and daily activities. You can read measurement system to see comparison of different engineering measurement unit systems and the history of their development. 

What is length measurement in engineering?

Length measurement in engineering is the procedure or technique carried out to estimate an object’s or structure’s size based on standard units (according to widely accepted rules) and mainly in terms of dimensions such as length, breadth or width, and height.

Generally, the measurements of an object’s physical properties are expressed differently from length; they include but are not limited to weight, heat, volume (the amount of 3-dimensional space occupied by an object), etc., all based on standard units. 

Measurement in engineering involves making comparisons between an estimated magnitude of a certain parameter and a predefined or established magnitude (which is a standard) of that dimension, physical property or parameter.

For instance, if we have to measure the length or height of someone’s body, we measure it with a tape that has an established or predefined markings and indicates various temperature values/magnitudes. Body temperature is measured with a thermometer that has a predefined scale and indicates various temperature values.

The two most widely used engineering measurement unit systems for lengths (and other physical properties of objects) are the “Metric System” (also known as the “International System of Units”) and the “United State Customary Units”. Both measurement systems consist of a number of units.

The metric system is the most popular standard that is widely used around the world, especially for expressing the sizes and dimensions of the lengths, heights, and widths of objects on engineering drawings.

Various kinds of professions (civil engineering, structural engineering, mechanical engineering, environmental engineering, architecture, industrial design, landscape design, manufacturing, etc.) use engineering measurement units and measurement systems on engineering drawings to communicate and document their designs.

The Metric System (International System of Units, or SI Units)

The present-day metric system is known as the “International System of Units” which is commonly called “SI Units”—an acronym from the French phrase “le Système International d’Unités”.

The International System of Units was established in 1960 after an international agreement was reached. Presently, it is the international standard that is widely used to express the sizes and dimensions of objects.

Although some countries still use the U.S. Customary Units to a less or great degree, all countries in the world have adopted the International System of Units.

The most widely used units of the Metric System (International System of Units) for estimating lengths are the kilometer (mm), the meter (m), and the millimeter (mm). The centimeter (cm) and the decimeter (dm) are also among the units in the Metric System, but they are rarely used on engineering drawings.

Some industries use a dual dimensioning system to express the units of the dimension sizes of objects on engineering drawings. For example, they could use “millimeter” and “inch” together on one drawing, even though millimeter is a unit that belongs to the Metric System (International System of Units) and inch on the other hand belongs to the U.S. Customary Units.

It is important to note that using a dual dimensioning system to express the units and sizes of object’s dimensions can get some people confused, especially as the sizes from any two different measurement systems may contain rounding errors whenever one unit is being converted into another.

Many creators of engineering drawings use Metric System units to express length/other dimensions and maintain consistency between different units that belong to the same measurement system. In standard practice, the following Metric System units and relationships are often used:

1 kilometer (km) = 1000 meters = 10,000 decimeters = 100,000 centimeters = 1,000,000 millimeters

1 meter (m) = 10 decimeters = 100 centimeters = 1000 millimeters

1 decimeter (dm) = 10 centimeters = 100 millimeters

1 centimeter (cm) = 10 millimeters = 0.1 decimeter

1 millimeter (mm) = 0.1 centimeter = 0.01 decimeter.

The United States Customary Units

The United States Customary Units (USCS or USC) is a measurement system that was formalized in 1832 and has been evolving and widely used in the United States since then. The USCS or USC was derived from the English units that were widely used in the British Empire before the United States became an independent nation.

The most widely used measurement units (for length) among the United States Customary Units are the mile (mi.), the foot (ft.), the inch (in.), and the yard (yd.). The pica (P.) and the point (p.) are also among the units in the United States Customary Units. However, they are often rarely used.

Although engineering drawings may use either measurement system (Metric System, or the United States Customary Units), they generally adhere to popularly accepted drawing standards and units.

Any length or dimensions expressed in the United States Customary Units can be easily converted to Metric System units in decimal or fractional form. In standard practice, the following units and relationships are often used:

1 mile (mi.) = 1760 yards = 5280 feet = 1.609 kilometers

1 yard (yd.) = 3 feet = 0.9144 meters = 914.4 millimeters

1 foot (ft. or ′) = 12 inches = 0.3048 meters = 304.8 millimeters

1 inch (in. or ″) = 6 pica = 25.4 millimeters = 2.54 centimeters

1 pica (P.) = 12 points = 4.233 millimeters

1 point (p.) = 0.3538 millimeters.

The Importance of Engineering Drawing (PDF Download Available)

It has taken centuries for the methods of engineering drawing to evolve into what we practice today. There are a number of areas where engineering drawing is very important, especially in engineering design processes that require documentation, visualization, and communication, amongst other areas discussed in this post.

The importance of engineering drawing includes but may not be limited to the following (NOTE: A free PDF copy of the importance of engineering drawing is available for download at the end of this post.):

1. Engineering drawing is important in education

Engineering drawing provides engineering and technology students and practicing professionals with knowledge of widely used techniques and standard practices employed worldwide in engineering fields such as mechanical, automotive, electrical, electronics, communication, civil, structural, architectural, aerospace, environmental, etc.

2. Engineering drawing is important in documentation

Apart from being used for effective communication and visualization, research and in other areas, engineering drawing is important for documentation, especially for archival and legal purposes when there is dispute in regard to construction works or the drawing plans they are produced from.

Documentation of drawings is crucial for present and future construction, manufacturing, or production needs, as anyone who comes across engineering drawing documents may benefit from them in one way or another.

3. Engineering drawing is important in visualization

Engineering drawing enhances designers’ ability to visualize (produce mental pictures of things that exist or are yet to exist physically) and develop new and greater ideas and turn them into very useful inventions that can solve so many people’s problems around the world.

Engineering drawing is important because it helps practitioners and professionals gain more inspiration and develop their imagination and skill or ability to solve more advanced technological problems.

Great designers like Leonardo da Vinci and Jules Verne had excellent visualization skills that produced pictures of objects in their minds before producing them in real life. Everything in life—computers, cars, gigantic pyramids, rockets, etc.—initially existed or conceived in the individual minds of the people who eventually constructed or produced them.

4. Engineering drawing is important in communication

Engineering drawing is important because it helps in conveying or communicating ideas from people, especially when it’s done without ambiguity and to such an extent that other people are able to understand or interpret it.

Engineering drawing enhances clear-cut communication and prevents misunderstanding between people associated with any engineering graphic design—like architects, engineers, etc. Clear understanding between parties makes it possible and easier for the same design ideas to be properly communicated, produced, and used in many countries.

5. Engineering drawing is important in manufacturing or production

Engineering drawing is important for shortening the design time/cycle and achieving the highest possible level of efficiency in production or manufacturing industries, helping practitioners to work more productively or efficiently, thereby saving time and reaching set goals.

Engineering drawing helps to identify design flaws during the design process, thereby ensuring safety and structural integrity and preventing failures or problems in the future.

Engineering drawing helps to effectively improve the efficiency of the design, construction, and maintenance planning processes which are very important; any effective planning process that considers various factors, such as environmental factors, social factors, natural factors, etc., would likely save a lot of manpower and time, and also prevent low efficiency and high error rate.

6. Engineering drawing is important to research work/studies

Engineering drawing helps in geometric studies to develop the movement of mechanical linkages, mechanical systematic diagrams, clearances, and general engineering structures; in addition, it helps to create technical information on proper positioning and installation of products or items. Installation drawings may include dimensional data, hardware descriptions, and information regarding general configuration on installation sites where control systems, electrical systems, hydraulic systems, and other types of systems exist.

Engineering drawing is used in intensive research to hasten the development of emerging technologies, discover alternative approaches for creating models, and invent more appropriate designs that could yield better outcomes in terms of product development and innovative design projects. Broadly speaking, engineering drawing helps to develop the spatial, imaginative, and multi-disciplinary research skills of everyone involved in research work.

Download PDF: The Importance of Engineering Drawing

Types of Lines in Engineering Drawing (PDF Free Download)

The types of lines in engineering drawing are fundamental and perhaps the most important thing in engineering drawing practice, especially as they illustrate how shapes and sizes of objects would appear in real life after they are constructed. The types of lines help to communicate, understand, and convey important messages that abide by engineering drawing standards.

A free PDF copy of the following types of lines in engineering drawing and their respective uses can be downloaded at the end of this page:

1. Break line

2. Center line (or, long/short-dashed thin line)

3. Chain line

4. Construction line

5. Continuous thick line

6. Continuous thin line

7. Cutting plane line (viewing plane or section line)

8. Dimension line

9. Extension line

10. Freehand break line (or continuous narrow irregular line)

11. Hatching lines (or section line)

12. Hidden line

13. Leader line

14. Long break line (or continuous thin straight line with zigzags)

15. Match line

16. Miter line (inclined projection line)

17. Phantom line

18. Stitch line

19. Symmetry line

20. Visible line

Download PDF: Types of Lines in Engineering Drawing

20 Types of Engineering Drawing Lines and Their Uses

Lines are perhaps the most important characteristic of engineering drawings because they illustrate how shapes and sizes of objects appear and would appear after they are constructed or produced.

The different types of lines engineering drawing lines help to convey important messages that abide by engineering drawing standards. Therefore, it is important to be acquainted with the different types of engineering drawing lines to read and create drawings and that other people can easily understand.

Twenty types of engineering drawing lines and their respective uses are as follows (NOTE: A free PDF copy of the engineering drawing lines discussed in this post can be downloaded on this page.):

 1. Break line

Break line is a type of engineering drawing line that is used to create breakouts on sections to shorten distances between parts of a drawing and give more clarity. Usually, three types of lines that have different line weights are used as break lines: long break line, short break line, and cylindrical break line.

Figure 1: Break line

 2. Center line (or, long/short-dashed thin line)

Center line is a type of engineering drawing line that is used to represent or locate the centers of circles, cylindrical surfaces, symmetrical areas/objects, tools, etc. Center lines are drawn as thin broken lines that have long and short dashes. In many instances, the long and short dashes may vary in length, but this depends on the scale or size of the drawing. Center lines could be extended and used as extension lines during dimensioning of objects or shapes.

Figure 2: Center line

3. Chain line

Chain line is a thin or thick broken or spaced parallel line used to indicate pitch lines (lines that show the pitch of gear teeth or sprocket teeth), developed views, the features in front of a cutting plane, or center lines. Usually, chain lines are applied at the beginning and end of long dashes, at center points as center lines, in dimensioning, or for other purposes.

Figure 3: Chain line

4. Construction Line

Construction line (which is a light thin line) is used to develop shapes and locations of features in engineering drawings. After using construction lines to develop thick visible outlines of objects, they can left on the sketches of many drawings or cleaned off with an eraser.

Figure 4: Construction line

5. Continuous thick line

Continuous thick line is the type of engineering drawing line that is used to represent visible edges and outlines of objects, shapes, and structures. They are usually dark and heavy solid lines which are very prominent in many drawings.

Figure 5: Continuous thick line

6. Continuous thin line

Continuous thin line is used to represent leader lines, extension lines, dimension lines, projection lines, hatching lines for cross sections, reference lines, imaginary lines of intersections, and short center lines.

Figure 6: Continuous thin line

7. Cutting plane line (viewing plane or section line)

Cutting plane line is the type of engineering drawing line that is used to designate the positions of cutting planes in sections, or during sectioning. Two types of cutting plane lines can be used: the first type is a dark line that consists of one long dash and two short dashes spaced alternately. Long dashes are usually drawn at any length between 20 and 40mm, or a little bit more, depending on the scale and size of the drawing. The short dashes are usually drawn approximately 3mm long, and spaced at 1.5mm (between dashes). The second type of cutting plane line consists of short dashes of equal lengths, approximately 6mm long, with a space (of length) of 1.5mm between each short dash.

Figure 7: Cutting plane line

8. Dimension line

Dimension line is a thin line that has arrowheads at its opposite ends and is used to represent the precise length, breadth, width, and height of objects.

Figure 8: Dimension line

9. Extension line

Extension line is a thin solid line that represents the extent (beginning and end) of a dimension in a drawing. Extension lines are usually drawn at approximately 1.5mm away from the outlines of objects and extended 3mm longer than the outermost arrowheads located at the ends of dimension lines.

Figure 9: Extension line side by side with dimension line

10. Freehand break line (or continuous narrow irregular line)

Freehand break line is the type of engineering drawing line that is drawn with freehand (i.e., by hand or without mechanical aids or devices) and used to indicate short breaks or irregular boundaries. It can also be used to set the limits of partial views or sections.

Figure 10: Freehand break lines

11. Hatching line (or section line)

Hatching or section line is used to indicate the sectional view or outlook of surfaces produced after making arbitrary cuts on an object. Hatching lines are usually thin lines drawn at an angle of 45° and equally spaced to indicate cut or sectioned material.

Figure 11: Hatching lines

12. Hidden line

Hidden line is the type of engineering drawing line that is used to describe features that cannot be seen when objects are viewed from a particular direction Hatching lines consist of short and equally spaced thin dash lines and spaces. The dashes are usually three to four times longer than the space between them.

It is recommended that the dashes used in hidden lines should be approximately 3 mm long and have a space of 1.0mm between each dash. On the other hand, the length of the dashes and the space between them can be slightly altered, depending on the scale and size of the drawing.

Figure 12: Hidden line

13. Leader line

Leader line is used to represent the dimensions of an object, feature, or structure whenever such dimensions are not clear enough after being placed beside objects, features, or drawn structures.

Figure 13: Leader line

14. Long break line (or continuous thin straight line with zigzags)

Long break line or continuous straight line with zigzags (see (B) below) shows continuity of partially interrupted views. They are very suitable for computer-aided design (CAD) drawings.

Figure 14: Long break lines

15. Match line

Match line is the type of engineering drawing line that is used to indicate a cut line between two or more drawings whenever the area on one drawing paper is too large for all the different drawings to occupy. Match lines are lines that are added to a conglomeration of drawing views to indicate where a view is split or where they have been merged.

In large or complex drawings (for instance, civil and electrical drawings) such as the electrical drawing in the figure below, only one entire view may not be fully or clearly expressed on a single sheet. Therefore, for drawings that extend from one sheet to another sheet, match lines are used to show how the drawing on one sheet matches with another one.

Figure 15: Match line used on an electrical drawing for a part of a building

16. Miter line (inclined projection line)

Miter line is used to project and transfer the dimensions (depths, heights, widths) of an object so that its side view can be shown at the right-hand and left-hand sides of the front or top view of the same object, depending on whether one uses first-, second-, third-, or fourth-angle drawing/projection, respectively).

Figure 16: Miter line

17. Phantom line

Phantom line is a thin line that consists of alternating long dashes that are separated by two short dashes and are often used to represent the direction of movement of an object or a part of an object in alternate positions. Phantom lines can also be used to indicate adjacent features or objects.

Figure 17: Phantom line

18. Stitch line

Stitch line is the type of engineering drawing line that is used to indicate the sewing or stitching lines on artifacts, objects, and even clothing. Stitch line consists of a series of very short dashes that are evenly spaced and approximately half the length of a typical dash or hidden line.

Figure 18: Stitch lines

19. Symmetry line

Symmetry line is an imaginary line that passes through the centers of areas, shapes, objects, and drawn structures; in most cases, symmetry lines divide objects into equal and similar-looking parts.

Figure 19: Symmetry lines

20. Visible line

Visible line is a thick and continuous bold line that is used to indicate the visible edges of objects. Visible lines usually stand out when compared with other lines.

Figure 20: Visible lines

The figures below are pictorial views of various types of lines used in engineering drawing:

Figure 21: Pictorial views of various types of lines

The Importance of Engineering Drawing Standards

Mankind has always been using drawings as a medium to express ideas and plans/intentions. The adage that “a picture is worth a thousand words” says a lot about mankind’s appreciation for the ability of drawings to communicate uncountable ideas without the need to waste too much energy discussing them. No need for too much talk; drawing tells it all!

Primitive engineering drawings were often crudely depicted and difficult to understand due to the lack of projection systems and standards that could carry everyone along. The way early engineering drawings (i.e., drawings that had no standards) were depicted often made it hard to guess the real sizes of parts in a drawing.

As time passed by, drafters/designers began to understand that it would be difficult to use drawings to communicate effectively and understand each other in the absence of agreed-upon standards for symbols, signs, letters, etc. This led to the development of “engineering drawing standards” or “drawing standards in engineering practice”.

The effectiveness of engineering drawing as a technical language has steadily increased over the past few decades up to modern times. Drawing standards have even been codified and stored in computer-aided design/drafting (CAD) systems which are often used to do all work usually undertaken by draughtsmen.

What are engineering drawing standards—or drawing standards in engineering?

Engineering drawing standards are sets of rules that govern how engineering drawings are or should be represented, especially on public or professional platforms. Engineering drawing standards consist of guidelines and technical definitions, including instructions for manufacturers and designers.

Drawing standards have become part and parcel of engineering field and practice, following a set of widely agreed standards that keep drawings in line and make technical graphics communication effective, nationally or regionally and globally. For over a century or more, many countries set up committees on engineering drawing standards or standardization to accomplish this goal.

Most countries have committees on engineering drawing standards that create and modify guidelines for dimensioning, abbreviations, tolerancing, representation of symbols, etc.

The British Standards Institution (BSI), which is the world’s first national organization on standards, was founded in 1901. The American National Standards Institute (ANSI) is a national body that sets and modifies drawing standards for engineering in the U.S.A. The American Society for Mechanical Engineers (ASME) is a professional organization which assists ANSI in developing drawing standards in engineering fields. In Canada, engineering drawing standards are established by the Canadian Standards Association (CSA). The Japanese Industrial Standards (JIS) runs the show in Japan. Leading members of each committee are part of the global committee on standardization known as the International Standards Organization (ISO).

Contemporary engineering drawing standards apply to the features of engineering (mechanical, civil, electrical, etc.), architectural, and technical drawings, including but may not be limited to:

• symbols
• dimensions
• abbreviations
• texts/lettering
• measurement/units
• layout characteristics
• border lines and title blocks
• plotting and plot styles
• tables
• file templates in CAD file storage.

However, the engineering drawing standards of today are not timeless or omnipotent. They have evolved over the years and may likely continue to do so as new technologies are invented and affect how engineering drawings should be produced to carry everyone along and save time.

The importance of engineering drawing standards

1. Engineering drawing standards are important for effective communication in engineering, as they give each drawing the same meaning to everyone who reads them, especially learned people or professionals.

Drawing standards ensure that each drawing can be interpreted by any number of people; thus, helping to ensure that drawings can be efficiently understood, reproduced, and reused by the general public.

2. Engineering drawing standards are important for consistency: they provide and maintain consistency in how drawings are expressed and models are constructed, thereby preventing unnecessary confusion, especially when drawing files are combined in CAD. Standards help to ensure that drawings can be manipulated in an unvarying or uniform manner.

3. Engineering drawing standards are important for achieving the highest possible level of efficiency or productivity in engineering practice: drawing standards help practitioners to work more productively or efficiently, thereby saving time and reaching set goals.

4. Engineering drawing standards are important for garnering or earning people’s trust, as they provide an all-round reliable and trustworthy platform that people rely on when it comes to engineered or related components or equipment. People trust more in all-round standards than in standards that are personal or limited in scope.

5. Engineering drawing standards are important for minimizing or cutting costs, especially in manufacturing industries where training and production process is simplified when procedures follow set standards that cut across whole nations, regions, continents, or the world.

6. Engineering drawing standards are important for interchangeability—i.e., they make it possible to exchange or interchange drawings/models across the world so that one model or part that is manufactured in one part of the world can fit with another part that is manufactured in another part of the world. Tolerance standards, for instance, can help to achieve this.

7. Engineering drawing standards are important for providing legal backup or security in cases that involve disputes, as they usually have legally appropriate information that is consistent on national and global scales and is backed up by one or more constitutions.