Types of Technical & Engineering Drawing Lines and Their Uses

The types and uses of various types of lines in technical & engineering drawing are as follows: (Note: Two diagrams at the end of this page illustrate how the various types of lines appear in drawings.)

Break lines

Break lines are used to create breakouts on sections in order to shorten distances between parts of a drawing and give more clarity. Three types of lines are normally used as break lines; they have different line weights: long break lines, short break lines, cylindrical break lines.

Center Lines (or, long/short-dashed thin lines)

Center lines are used to locate or represent the centers of tools, circles, cylindrical surfaces or volumes, and symmetrical areas/objects, etc. Center lines are drawn as thin broken lines that have long and short dashes. In many instances, the long and short dashes vary in length; however, 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.

Chain lines

Chain lines are broken or spaced parallel lines used to indicate either pitch lines (lines that show the pitch of gear teeth or sprocket teeth), center lines, developed views, or the features in front of a cutting plane. 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.

Construction Lines

Construction lines (light thin lines) are used to develop shapes and locations of features in technical & engineering drawings. After using construction lines to develop thick visible outlines of objects, they are either left on the sketches of many drawings, or cleaned off with an eraser.

Continuous thick lines

Continuous thick lines are used to represent visible edges and outlines of objects, shapes, and structures on paper or computer. They are usually dark and heavy solid lines which are very prominent in many drawings.

Continuous thin lines

Continuous thin lines are used to represent dimension lines, extension lines, projection lines, hatching lines for cross sections, leader lines, reference lines, imaginary lines of intersections, and short center lines.

Cutting plane lines (viewing plane lines)

Cutting plane lines are used to indicate 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; it depends on the scale and size of the drawing. On the other hand, 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.

Dimension lines

Dimension lines are thin lines that have arrowheads at their opposite ends; they are used to show the precise length, breadth, width, and height of objects.

Click here and download illustrations for the most popular types of lines used in technical and engineering drawing

Download PDF: Types of Technical & Engineering Drawing Lines and Their Uses

Download PDF: Definition and Types of Technical Drawing

Extension lines

Extension lines are thin solid lines that are used to show 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.

Freehand Break lines (or continuous narrow irregular lines)

Freehand break lines are lines drawn with freehand, and used to indicate short-breaks or irregular boundaries; they can be used to set the limits of partial views or sections.

Hatching lines (or section lines)

Hatching or section lines are used to indicate the sectional view or outlook of surfaces produced as a result of making arbitrary cuts on an object. Hatching lines are usually thin lines that are drawn at an angle of 45° and equally spaced.

Hidden Lines

Hidden lines are used to describe features that cannot be seen when objects are viewed from a particular direction; they 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.

Leader lines

Leader lines are used to show the dimensions of an object, feature, or structure whenever such dimensions are not clear enough after being placed beside objects, features, or drawn structures.

Long Break line (or continuous thin straight lines with zigzags)

Long break lines (or continuous straight lines with zigzags) show continuity of partially interrupted views; they are very suitable for computer-aided design (CAD) drawings.

Symmetry Lines

Symmetry lines are imaginary lines that pass through the centers of areas, shapes, objects, and drawn structures; in most cases, symmetry lines divide objects into equal and similar-looking parts.

Visible Lines

Visible lines are thick and continuous bold lines that are used to indicate the visible edges of objects. They usually stand out when compared with other lines.

The figures below are pictorial views of various types of lines used in technical & engineering drawing:

Figure 1: A drawing that shows various types of lines

Figure 2: A drawing that shows various types of lines

Thank you for reading.

 

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For further reading and study of topics on technical and engineering drawings/graphics—which is essential for your education/future as an engineer/technologist and—we advise that you make a habit of reading good books.

It’s possible to get a good book from a friend or purchase it either from a local bookstore (offline) or online. In case you’d be interested in purchasing, we have six high-quality technical & engineering drawings/graphics books (eBooks/PDF books) for sale at cheap prices.

Continue scrolling down and you’ll come across their respective titles, number of pages, and lists of chapters. Each book is available for purchase at a cost of $5 (or 2,500 Naira) per book; if you wish to purchase all books, you’ll get a discount of $5 (2,500 Naira) and purchase 6 books for $25 (12,000 Naira) instead of $30 (15,000 Naira).

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The titles of the books (arranged in decreasing order of priority [from 1 to 6]—based on our assessment) and their respective number of pages and titles of chapters are as follows:

1. Technical Graphics Communication, 4th Edition, by Gary R. Bertoline, Eric N. Wiebe, Nathan W. Hartman, William A. Ross (1335 pages), 2009

Chapter 1: Introduction to Graphics Communication, pg.5

Chapter 2: The Engineering Design Process, pg.27

Chapter 3: Design in Industry, pg.46

Chapter 4: The Role of Technical Graphics in Production, Automation, and Manufacturing Processes, pg.109

Chapter 5: Design & Visualization, pg.135

Chapter 6: Technical Drawing Tools, pg.187

Chapter 7: Sketching and Text, pg.237

Chapter 8: Engineering Geometry and Construction, pg.305

Chapter 9: Three-dimensional Modeling, pg.399

Chapter 10: Multiview Drawings, pg.488

Chapter 11: Axonometric and Oblique Drawings, pg.577

Chapter 12: Perspective Drawings, pg.631

Chapter 13: Auxiliary Views, pg.652

Chapter 14: Fundamentals of Descriptive Geometry, pg.691

Chapter 15: Intersections and Developments, pg.716

Chapter 16: Section Views, pg.759

Chapter 17: Dimensioning and Tolerancing Practices, pg.818

Chapter 18: Geometric Dimensioning and Tolerancing (GDT), pg.875

Chapter 19: Fastening Devices and Methods, pg.908

Chapter 20: Working Drawings, pg.949

Chapter 21: Technical Data Presentation, pg.1064

Chapter 22: Mechanisms: Gears, Cams, Bearings, and Linkages, pg.1105

Chapter 23: Electronic Drawings, pg.1146

Chapter 24: Piping Drawings, pg.1163

Chapter 25: Welding Drawings, pg.1187

2. Technical Drawing with Engineering Graphics, 15th Edition, by Frederick E. Giesecke, Shawna Lockhart, Marla Goodman, Cindy M. Johnson (1077 pages), 2016

Chapter 1: The World-wide Language for Graphic Design, pg.2

Chapter 2: Layouts and Lettering, pg.30

Chapter 3: Visualization and Sketching, pg.62

Chapter 4: Geometry for Modeling and Design, pg.124

Chapter 5: Modeling and Design, pg.170

Chapter 6: Orthographic Projection, pg.234

Chapter 7: 2D Drawing Representation, pg.284

Chapter 8: Section Views, pg.326

Chapter 9: Auxiliary Views, pg.362

Chapter 10: Modeling for Manufacture, pg.414

Chapter 11: Dimensioning, pg.502

Chapter 12: Tolerancing, pg.546

Chapter 13: Threads, Fasteners, and Springs, pg.592

Chapter 14: Working Drawings, pg.636

Chapter 15: Drawing Control and Data Management, pg.710

Chapter 16: Gears and Cams, pg.730

Chapter 17: Electronic Diagrams, pg.756

Chapter 18: Structural Drawing, pg.780

Chapter 19: Landform Drawings, pg.808

Chapter 20: Piping Drawings, pg.828

Chapter 21: Welding Representation, pg.846

Chapter 22: Axonometric Projection, pg.W870

Chapter 23: Perspective Drawings, pg.W900

3. Engineering Drawing & Design, 6th Edition, by David A. Madsen and David P. Madsen (1104 pages), 2017

Chapter 1: Introduction to Engineering Drawing and Design, pg.2

Chapter 2: Drafting Equipment, Media, and Reproduction Methods, pg.39

Chapter 3: Computer-Aided Design and Drafting (CADD), pg.61

Chapter 4: Manufacturing Materials and Processes, pg.109

Chapter 5: Sketching Applications, pg.162

Chapter 6: Lines and Lettering, pg.181

Chapter 7: Drafting Geometry, pg.205

Chapter 8: Multiviews, pg.228

Chapter 9: Auxiliary Views, pg.259

Chapter 10: Dimensioning and Tolerancing, pg.277

Chapter 11: Fasteners and Springs, pg. 347

Chapter 12: Sections, Revolutions, and Conventional Breaks, pg.387

Chapter 13: Geometric Dimensioning and Tolerancing, pg.409

Chapter 14: Pictorial Drawings and Technical Illustrations, pg.495

Chapter 15: Working Drawings, pg.526

Chapter 16: Mechanisms: Linkages, Cams, Gears, and Bearings, pg.561

Chapter 17: Belt and Chain Drives, pg.601

Chapter 18: Welding Processes and Representations, pg.617

Chapter 19: Precision Sheet Metal Drafting, pg.644

Chapter 20: Electrical and Electronic Drafting, pg.669

Chapter 21: Industrial Process Piping, pg.717

Chapter 22: Structural Drafting, pg.773

Chapter 23: Heating, Ventilating, and Air-conditioning (HVAC) and Pattern Development, pg.847

Chapter 24: Civil Drafting, pg.899

Chapter 25: The Engineering Design Process, pg.950

Engineering Drawing and Design Student Companion Website, pg.973

4. Engineering Design and Graphics with SolidWorks by James D. Bethune (829 pages), 2017

Chapter 1: Getting Started, pg.1

Chapter 2: Sketch Entities and Tools, pg.41

Chapter 3: Features, pg.123

Chapter 4: Orthographic Views, pg.225

Chapter 5: Assemblies, pg.299

Chapter 6: Threads and Fasteners, pg.375

Chapter 7: Dimensioning, pg.439

Chapter 8: Tolerancing, pg.509

Chapter 9: Bearings and Fit Tolerances, pg.605

Chapter 10: Gears, pg.639

Chapter 11: Belts and Pulleys, pg.699

Chapter 12: Cams, pg.725

Chapter 13: Projects, after pg.774

5. Interpreting Engineering Drawings, 8th Edition, by Theodore J. Branoff (530 pages), 2016

Unit 1: Introduction: Line Types and Sketching, pg.1

Unit 2: Lettering and Title Blocks, pg.11

Unit 3: Basic Geometry: Circles and Arcs, pg.15

Unit 4: Working Drawings and Projection Theory, pg.22

Unit 5: Introduction to Dimensioning, pg.39

Unit 6: Normal, Inclined, and Oblique Surfaces, pg.52

Unit 7: Pictorial Sketching, pg.67

Unit 8: Machining Symbols and Revision Blocks, pg.78

Unit 9: Chamfers, Undercuts, Tapers, and Knurls, pg.86

Unit 10: Sectional Views, pg.91

Unit 11: One- and Two-View Drawings, pg.110

Unit 12: Surface Texture, pg.117

Unit 13: Introduction to Conventional Tolerancing, pg.130

Unit 14: Inch Fits, pg.142

Unit 15: Metric Fits, pg.150

Unit 16: Threads and Fasteners, pg.161

Unit 17: Auxiliary Views, pg.181

Unit 18: Development Drawings, pg.190

Unit 19: Selection and Arrangement of Views, pg.196

Unit 20: Piping Drawings, pg.202

Unit 21: Bearings, pg.214

Unit 22: Manufacturing Materials, pg.220

Unit 23: Casting Processes, pg.232

Unit 24: Violating True Projection: Conventional Practices, pg.249

Unit 25: Pin Fasteners, pg.264

Unit 26: Drawings for Numerical Control, pg. 274

Unit 27: Assembly Drawings, pg.280

Unit 28: Structural Steel, pg.289

Unit 29: Welding Drawings, pg.294

Unit 30: Groove Welds, pg.305

Unit 31: Other Basic Welds, pg.315

Unit 32: Spur Gears, pg.328

Unit 33: Bevel Gears and Gear Trains, pg.337

Unit 34: Cams, pg.347

Unit 35: Bearings and Clutches, pg.353

Unit 36: Ratchet Wheels, pg.362

Unit 37: Introduction to Geometric Dimensioning and Tolerancing, pg.368

Unit 38: Features and Material Condition Modifiers, pg.380

Unit 39: Form Tolerances, pg.394

Unit 40: The Datum Reference Frame, pg.402

Unit 41: Orientation Tolerances, pg.415

Unit 42: Datum Targets, pg.432

Unit 43: Position Tolerances, pg.440

Unit 44: Profile Tolerances, pg.461

Unit 45: Runout Tolerances, pg.469

6. Architectural Graphic Standards Student Edition, 12th Edition, by The American Institute of Architects (689 pages), 2017

Chapter 1: Functional Planning, pg.3

Chapter 2: Environment, pg.31

Chapter 3: Resilience in Buildings. Pg.53

Chapter 4: Architectural Construction Documentation, pg.77

Chapter 5: Concrete, pg.93

Chapter 6: Masonry, pg.107

Chapter 7: Metals, pg.125

Chapter 8: Wood, pg.141

Chapter 9: Glass, pg.165

Chapter 10: Element A: Substructure, pg.176

Chapter 11: Element B: Shell, pg.203

Chapter 12: Element C: Interiors, pg.363

Chapter 13: Element D: Services, pg.427

Chapter 14: Element E: Equipment and Furnishings, pg.517

Chapter 15: Element F: Special Construction, pg.565

Chapter 16: Element G: Sitework, pg.581

Appendices, pg.627

 

Thank you.

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