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