359387224 engineering drawing cecil jensen jay d helsel dennis r short engineering drawing and design mcgraw hill 2008 pdf

Contents
Preface

Computer-Integrated Manufacturing (CIM)

xii

Acknowledgments

xiv

About the Authors

xv

Review and Assignments

1

PART

BASIC DRAWING AND DESIGN
Chapter

1

Chapter

1

1-1 The Language of Industry
Drawing Standards 3

1-3 The Drafting Office

2

2

1-2 Careers in Engineering Graphics 4
The Student 4
Places of Employment 4
Training, Qualifications, and Advancement
Employment Outlook S

3 ""~11·.

--------·

3-1 Drawing Media and Format
Drawing Media 32
Standard Drawing Sizes 32
Drawing Format 33
3-2 Filing and Storage
Filing Systems 36
CAD 37

S

Review and Assignments

Chapter

15

4

42

!IBIIB·-----·

<•:11·

Basic Drafting Skills

11111111------·

f;~JS·

Computer-Aided Drawing (CAD}
2-1 Overview

36

5

Review and Assignments

2

32

3-3 Drawing Reproduction 38
Reproduction Equipment 38

1-4 Board Drafting 7
Drafting Furniture 7
Drafting Equipment 7

Chapter

30

Drawing Media, Filing, Storage,
and Reproduction 32

:?~i''IJLW.Ia_ _ _ _ _ __

Engineering Graphics as a Language

29

18

18

2-2 Components of a CAD System
Hardware 19
Software 24

19

2-3 Communication Environment 27
Local Area Networks (LANs) 27
Wide Area Networks (WANs) and the World Wide
Web (WWW) 27
Cooperative Work Environments 28
2-4 Computer-Aided Manufacturing (CAM)
Computer Numerical Control 28
Robotics 28

28

43

4-1 Straight Line Work, Lettering, and Erasing 43
Engineering Drawing Standards and Conventions 43
Board Drafting 44
CAD 54
Coordinate Input 50
4-2 Circles and Arcs 51
Center Lines 51
CAD 51
Drawing Circles and Arcs
CAD 53

51

4-3 Drawing Irregular Curves
CAD 54

53

4-4 Sketching 54
Sketching Paper 54
Basic Steps to Follow When Sketching
Review and Assignments

57

58
iii


iv

Contents

Chapter

5 ';~'~Il ,;.- - - - - - - -

Applied Geometry
5-2 Arcs and Circles

5-4 Ellipse

70

Chapter

73

77

132

132

Dimensioning Auxiliary Views

134

7-2 Circular Features in Auxiliary Projection

Helix 77
Parabola 78

7-3 Multi-Auxiliary-View Drawings

Review and Assignments

6

7 ':!li~l '.11.- - - - - - - - ·

7-1 Primary Auxiliary Views

76

103

105

Auxiliary Views and Revolutions

75

5-5 Helix and Parabola

Chapter

Review and Assignments

70

5-1 Beginning Geometry: Straight Lines

5-3 Polygons

6-15 Intersections of Unfinished Surfaces

7-4 Secondary Auxiliary Views

79

' ' IBB·-----·

Theory of Shape Description

86

6-1 Orthographic Representations

86

Theory of Shape Description 86
Orthographic Representations 86
Methods of Representation 87

7-5 Revolutions

136

137

140

Reference Planes
Revolutions

140

140

The Rule of Revolution

142

True Shape of an Oblique Surface Found

by Successive Revolutions 142
Auxiliary Views and Revolved Views 143
True Length of a Line

144

7-6 Locating Points and Lines in Space

145

Points in Space 145
Lines in Space 145

CAD Coordinate Input for Orthographic
Representation 90

Spacing the Views

92

True Length of an Oblique Line by Auxiliary
View Projection 146

Use of a Miter Line

93

Point on a Line

6-2 Arrangement and Construction of Views

CAD

92

7-7 Planes in Space

6-3 All Surfaces Parallel and All Edges
and Lines Visible 94

6-5 Inclined Surfaces

96

6-6 Circular Features

96

Center Lines

146

Point-on-Point View of a Line

94

6-4 Hidden Surfaces and Edges

Locating a Line in a Plane

95

7-8 Establishing Visibility of Lines in Space

6-8 One- and Two-View Drawings

6-9 Special Views

98

Visibility of Lines and Surfaces by Observation

7-9 Distances between Lines and Points
Distance from a Point to a Line

99

7-10 Edge and True View of Planes

99

Planes in Combination

6-10 Conventional Representation
of Common Features 101
101

Square Sections

101

6-11 Conventional Breaks

Edge Lines of Two Planes

Transparent Materials

102

Chapter

102

6-13 Cylindrical Intersections
6-14 Foreshortened Projection

'~<,,....~

177

8-1 Basic Dimensioning

102
102

163

'.\;>i';·--------

Basic Dimensioning

102

Holes Revolved to Show True Distance from Center

8

160
160

161

Review and Assignments
102

154

157

The Angle a Line Makes with a Plane

6-12 Materials of Construction

154

158

7-11 Angles between Lines and Planes

101

Repetitive Parts

153

154

Shortest Distance between Two Oblique Lines

Partial Views 99
Rear Views and Enlarged Views

Repetitive Details

152

Visibility of Oblique Lines by Testing 152
Visibility of Lines and Surfaces by Testing 152

98
99

Two-View Drawings

148

Locating the Piercing Point of a Line and a
Plane-Auxiliary View Method 1SO

97

View Selection 98
One-View Drawings

148

148

Locating a Point on a Plane 149
Locating the Piercing Point of a Line and a
Plane-Cutting-Plane Method 150

96

6-7 Oblique Surfaces

135

Dimensioning

177

177

Units of Measurement

181


Contents

Dual Dimensioning

9-2 Two or More Sectional Views on
One Drawing 238

182

182

Angular Units

Reading Direction

183

9-3 Half-Sections
183

Basic Rules for Dimensioning
Symmetrical Outlines 184
Reference Dimensions
Operational Names

Threaded Assemblies

184

241

Section Lining on Assembly
Drawings 241

184

184

Abbreviations

240
240

9-5 Assemblies in Section

184

Not-to-Scale Dimensions

239

9-4 Threads in Section

8-2 Dimensioning Circular Features
Diameters 185
Radii 186

185

9-6 Offset Sections

243

8-3 Dimensioning Common Features

189
189

9-7 Ribs, Holes, and Lugs in Section
Ribs in Sections 243
Holes in Sections 243
Lugs in Section 243
9-8 Revolved and Removed Sections
Placement of Sectional Views 245

245

Repetitive Features and Dimensions
Chamfers

189

Slopes and Tapers

190

191

Knurls

9-9 Spokes and Arms in Section

191
Undercuts 192
Limited Lengths and Areas 192
Wire, Sheet Metal, and Drill Rod 192
Formed Parts

8-4 Dimensioning Methods

9-11 Phantom or Hidden Sections
9-12 Sectional Drawing Review
Review and Assignments

193
193
True-Position Dimensioning 193
Chain Dimensioning 193
Datum or Common-Point Dimensioning
Polar Coordinate Dimensioning

PART

202
202
Basic Hole System 204
Basic Shaft System 205
Preferred Metric Limits and Fits 205
Standard Inch Fits

208

211

Review and Assignments

Chapter

Sections

9

209

209

211

Machined Surfaces

216

:~:B:!I:• • • • • • • • •

235

9-1 Sectional Views
cutting-Plane Lines
Full Sections
Section Lining

237
237

235
235

FASTENERS, MATERIALS, AND FORMING
PROCESSES 269

lQ

.,~:.;,gill_ _ _ _ __

Threaded Fasteners

Interchangeability of Parts

Surface Texture Symbol

2

Chapter

Surface Texture Characteristics

249

200

8-6 Fits and Allowances 201

Fits 201
Allowance 201
Description of Fits 201

8-7 Surface Texture

248

---------·.~·
195

195

Additional Rules for Dimensioning

248
248

193

Chordal Dimensioning

8-5 Limits and Tolerances
Key Concepts 196
Tolerancing 197

247

9-10 Partial or Broken-Out Sections

192

Rectangular Coordinate Dimensioning

Application

242

270

10-1 Simplified Thread Representation 270
Screw Threads 271
Thread Forms 271
Thread Representation 271
Right- and Left-Hand Threads 272
Single and Multiple Threads 272
Simplified Thread Representation 273
Threaded Assemblies 273
Inch Threads 273
Metric Threads 276
Pipe Threads 278
10-2 Detailed and Schematic Thread
Representation 278
Detailed Thread Representation 278
Threaded Assemblies 279
Schematic Thread Representation 279
10-3 Common Threaded Fasteners 280
Fastener Selection 280
Fastener Definitions 281
Fastener Configuration 281

Head Styles 281
Property Classes of Fasteners 282

v


vi

Contents

Drawing a Bolt and Nut
Studs 285
Washers

284

Chapter

285

Terms Related to Threaded
Fasteners 285
Specifying Fasteners

Setscrews

Ferrous Metals
Cast Iron 341

287

287
287

Sealing Fasteners

290

290

291

Special Tapping Screws

SAE and AISI-Systems of Steel Identification
High-Strength Low-Alloy Steels 348
Low- and Medium-Alloy Steels 348
Stainless Steels 348
Free-Machining Steels

291

Review and Assignments

12-3 Nonferrous Metals

295

11

·:JI.·- - - - - - - ·

Miscellaneous Types of Fasteners
11-1 Keys, Splines, and Serrations
Keys

305

305

Splines and Serrations

11-2 Pin Fasteners

306

349

309

312

Spring Clips

11-5 Rivets

351
351

352

352

Machining 3S2
Material Selection

354

357

Material and Characteristics
Kinds of Rubber 357

315

Assembly Methods

Standard Rivets 317
Large Rivets 317

Chapter

13-1 Metal Castings

323

Resistance-Welded Fasteners

323

323

11-7 Adhesive Fastenings
Adhesion versus Stress
Joint Design 325

364

364

Forming Processes
Casting Processes
Selection of Process

325

11-8 Fastener Review for Chapters 10
and 11 327
Review and Assignments

364
364
368

Design Considerations 369
Drafting Practices 371

325

328

359

13 .~Ill·,- - - - - - - ·

Forming Processes

318

Arc-Welded Studs

358

Review and Assignments

Rivets for Aerospace
Equipment 317
Small Rivets 318

357

357

Design Considerations

11-6 Welded Fasteners

352

352

Forming Processes

12-5 Rubber
313
315

317

Blind Rivets

351

Thermosetting Plastics

313

Types of Springs
Spring Drawings

351

Beryllium

Thermoplastics

Stamped Retaining Rings 312
Wire-Formed Retaining Rings 313
Spiral-Wound Retaining Rings 313

11-4 Springs

350

Titanium

12-4 Plastics

311

11-3 Retaining Rings

Magnesium
Zinc 351

Precious Metals

Semipermanent Pins

349

Copper 350
Nickel 350

Refractory Metals

308

Quick-Release Pins

305

345

348

Manufacturing with Metals
Aluminum 349

Chapter

343

Carbon Steels 343
Steel Specification 343

10-5 Fasteners for Light-Gage Metal, Plastic,
and Wood 291
Tapping Screws

343

Carbon and Low-Alloy Cast Steels
High-Alloy Cast Steels 343

Captive or Self-Retaining Nuts
Inserts 290

341

341

12-2 Carbon Steel

Keeping Fasteners Tight
Locknuts 288

341

12-1 Cast Irons and Ferrous Metals

286

10-4 Special Fasteners

12 :~.~:;·a,- - - - - •

Manufacturing Materials

Casting Datums 373
Machining Datums 374

13-2 Forgings

375

Closed-Die Forging

375

vii

Contents

General Design Rules
Drafting Practices

13-3 Powder Metallurgy
13-4 Plastic Molded Parts
Single Parts 380

380

15-2 Curved Surfaces in Isometric 464
Circles and Arcs in Isometric 464
Drawing Irregular Curves in Isometric

Review and Assignments

PART

387

3

WORKINCi DRAWINGS AND DESICiN
Chapter

397

14

Detail and Assembly Drawings

14-2 Functional Drafting
Procedural Shortcuts

403

405

Detail Drawing Requirements
Drawing Checklist

405

Oblique Sectioning 472
Treatment of Conventional Features

14-5 Drawing Revisions

410

411

14-8 Detail Assembly Drawings
14-9 Subassembly Drawings

Image Generation 488
Data Extraction 489

491

412

413

415

Review and Assignments

416

Chapter

16 :~.~·····------·

Geometric Dimensioning and Tolerancing

15

Pictorial Drawings 457
15-1 Pictorial Drawings

484

Surface Modeling 486
Solid Modeling 486

Review and Assignments

411

14-7 Exploded Assembly Drawings

Chapter

484

Wire-Frame Modeling

Assembly Drawings for Catalogs

480

483

15-8 Solid Modeling

Design Assembly Drawings 410
Installation Assembly Drawings 411
Item List

402

15-6 Parallel, or One-Point, Perspective 474
Perspective Projection
474
Types of Perspective Drawings 475
Parallel, or One-Point, Perspective 476

CAD

407

409

14-6 Assembly Drawings

402

472

Basic Steps to Follow for Angular- Perspective
Sketching (Fig. 15-58) 483

405
405

14-4 Multiple Detail Drawings

471

15.7 Angular, or Two-Point, Perspective
Angular-Perspective Sketching 481

405

Qualifications of a Detailer
Manufacturing Methods

470

Basic Steps to Follow for Parallel Perspective
Sketching (Fig. 15-47) 477

404

14-3 Detail Drawings

15-4 Oblique-Projection 467
Inclined Surfaces 468
Oblique Sketching 468

15-5 Common Features in Oblique
Circles and Arcs 471

Reducing the Number of Drawings Required
Reproduction Shortcuts

15-3 Common Features in Isometric 465
Isometric Sectioning 465
Fillets and Rounds 467
Threads 467
Break Lines 467
Isometric Assembly Drawings 467

Dimensioning Oblique Drawings

400

400

Simplified Representations in Drawings

464

Basic Steps to Follow for Oblique
Sketching (Fig. 15-29) 470

398

14-1 Drawing Quality Assurance 398
Review Considerations 398
Drawing Considerations 399
Fabrication Considerations 400
Assemble Considerations 400

Photodrawings

460

Isometric Sketching 461
Basic Steps to Follow for Isometric
Sketching (Fig. 15-12) 462

383
386

Drawings

460

Dimensioning Isometric Drawings

380
380

Design Considerations

Assemblies

Nonisometric Lines

376

377

457
457
460

16-1 Modern Engineering Tolerancing
Basic Concepts 511
Size of Dimensions 511

Axonometric Projection

Interpretation of Drawings and
Dimensions 513

Isometric Drawings

Assumed Datums

513

510

510


viii

Contents

16-2 Geometric Tolerancing
Feature Control Frame

S17

Profile Symbols

517

Placement of Feature Control Frame
Form Tolerances 518
Straightness 519

16-3 Flatness

517

Coplanarity

S22

Concentricity

16-4 Straightness of a Feature of Size

522

16-16 Positional Tolerancing for Multiple Patterns
of Features S84
Composite Positional Tolerancing

S29

529

16-6 Orientation Tolerancing of Flat Surfaces
Reference to a Datum

587

Floating Fasteners 591
Calculating Clearance 592
Fixed Fasteners 592
Unequal Tolerances and Hole Sizes
Coaxial Features 594

S3S

535

Angularity Tolerance 535
Perpendicularity Tolerance 535
Parallelism Tolerance 535
Examples of Orientation Tolerancing
Control in Two Directions 536

Perpendicularity Errors

Review and Assignments

543

537

S42

Chapter

17 :~ ~ · - - - - - - - -

17-1 Two-Axis Control Systems

16-10 Projected Tolerance Zone

Review and Assignments

S6S

Chapter

636

18 ·~;g··.- - - - - - - -

Welding Drawings

641

18-1 Designing for Welding
Welding Processes

18-2 Welding Symbols

641

641

643

The Design of Welded Joints

18-3 Fillet Welds
S69

633

633

SS9

S61

Circularity 565
Cylindricity 567

629

Dimensioning and Tolerancing

Datum Target Symbol 562
Identification Targets 562
Targets Not in the Same Plane 563
Partial Surfaces as Datums 565
Dimensioning for Target Location 565

16-12 Circularity and Cylindricity

629

Computer Numerical Control (CNC) 629
Dimensioning for Numerical Control 630
Dimensioning for a Two-Axis Coordinate
System 631

17-2 Three-Axis Control Systems

S49

Tolerancing Methods 549
Coordinate Tolerancing 550
Positional Tolerancing 553

S9S

595

S98

Drawings for Numerical Control

Control in Two Directions 543
Control on an MMC Basis 543
Internal Cylindrical Features 545
External Cylindrical Features 548

16-13 Profile Tolerancing

595

S37

16-8 Orientation Tolerancing for Features of Size

16-9 Positional Tolerancing

594

When to Use Geometric Tolerancing
Basic Rules 595

535

Parts with Cylindrical Datum Features
RFS and MMC Applications 538
Angularity Tolerance 543
Parallelism Tolerance 543
Perpendicularity Tolerance

S91

16-18 Summary of Rules for Geometric Tolerancing

16-7 Datum Features Subject to Size Variation

569

580

16-17 Formulas for Positional Tolerancing

Datums for Geometric Tolerancing
Three-Plane System 531
Identification of Datums 532

Profiles

575

Noncircular Features at MMC

524

529

16-11 Datum Targets

574

16-1S Positional Tolerancing for Noncylindrical
Features S80

Applicability of RFS, MMC, and LMC 525
Straightness of a Feature of Size 527

16-S Datums and the Three-Plane Concept

571

S74

Coaxiality 577
Symmetry 578
Runout 578

S23

Features of Size 523
Material Condition Symbols (Modifiers)

569

Profile-of-a-Surface Tolerance

16-14 Correlative Tolerances

Flatness of a Surface 522
Flatness per Unit Area 522
Two or More Flat Surfaces in One Plane

Datums

569

Profile-of-a-Line Tolerance

6SO

Fillet Weld Symbols 650
Size of Fillet Welds 653

648


ix

Contents

18-4 Groove Welds

654

Use of Break in Arrow of Bevel and J-Groove Welding
Symbols 655
Groove Weld Symbols
Groove Joint Design

18-5 Other Basic Welds
Plug Welds 662
Slot Welds 663
Spot Welds 664
Seam Welds

Design of Roller Chain Drives

20-3 Gear Drives

660

Spur Gears

Flanged Welds

719

730
730

20-4 Power-Transmitting Capacity
of Spur Gears 736
Selecting the Spur Gear Drive 736

668

Surfacing Welds
Stud Welds

655
662

20-2 Chain Drives 717
Basic Types 717
Sprockets 719

20-5 Rack and Pinion

669
670

20-6 Bevel Gears

738

739

Working Drawings of Bevel Gears

671

Review and Assignments

20-7 Worm and Worm Gears

673

740

740

Working Drawings of Worm and Worm Gears

19 ,z~:•···~-------·

Chapter

Design Concepts

686

19-1 The Design Process 686
The Design Process 686

20-8 Comparison of Chain, Gear, and
Belt Drives 744
Chains 744
Gears 744
Belts 744

Chain Drives Compared with Gear Drives
Chain Drives Compared with Belt Drives

The Engineering Approach to Successful
Design 687

Conclusion

Part Specifications

Review and Assignments

688

Do's and Don'ts for Designers

19-2 Assembly Considerations
Cost of Assembly 690
Attachments 691
Design Checklist 697

690

Chapter

697

698

699

19-4 Project Management

699

699

702

703

21-2 Bearings

4

759

Shaft and Housing Fits
Bearing Symbols

Chapter

707

767
769

21-6 Static Seals and Sealants 775
0-Ring Seals 775
Flat Nonmetallic Gaskets 776

Metallic Gaskets 777
Sealants 777
Exclusion Sea Is 777

708

20-1 Belt Drives
Flat Belts 708
Conventional Flat Belts

709
710
How to Select a Light-Duty V-Belt Drive

763
763

21-S Lubricants and Radial Seals
Lubricants 769
Grease and Oil Seals 770
Radial Seals 771

20

Belts, Chains, and Gears

760

766

21-4 Premounted Bearings

POWER TRANSMISSIONS

V-Belts

712

756

759

Bearing Classifications

PART

756

21-1 Couplings and Flexible Shafts
Couplings 756
Flexible Shafts 758

21-3 Antifriction Bearings
Bearing Loads 760
Ball Bearings 760
Roller Bearings 762
Bearing Selection 763

702

Review and Assignments

746

21 ';;,f~l!l~,·-------·

Plain Bearings

Online Project Management
Assignments

745

Couplings, Bearings, and Seals

Concurrent Engineering through Computers
Green Engineering

744
745

689

Design Approach to a Fabricated Structure

19-3 Concurrent Engineering

740

Review and Assignments

780


Contents

X

Chapter

22

23-11 Stampings

847

Design Considerations

Cams, Linkages, and Actuators
22-1 Cams, Linkages, and Actuators
Cam Nomenclature

792

Review and Assignments

792

793

Chapter

Cam Followers 794
Cam Motions 794
Cam Displacement Diagrams

798

798

799

Conjugate Cams 800
Timing Diagrams 801
Dimensioning Cams
Cam Size 804

808

22-6 Linkages

810

801

Pipe Drawings

867

Kinds of Pipes

867

871

Piping Drawings

24-2 Isometric Projection of Piping Drawings
80S

24-3 Supplementary Piping Information

Chapter
811

Systems Having Linkages and Cams

887

The Building Process

813

Review and Assignments

877

Structural Steel-Plain Material 888
Structural Drawing Practices 893

87S

2S-2 Beams

894

Assembly Clearances

5

2S-3 Standard Connections

SPECIAL FIELDS OF DRAFTING

Bolted Connections

823

2S-4 Sectioning

23

896

898

898

90S

Bottom Views

905

Elimination of Top and Bottom Views
Right- and Left-Hand Details 906

Developments and Intersections
23-1 Surface Developments

895

Simple Square-Framed Beams

------------·t''
Chapter

877

------

25

2S-1 Structural Drafting

812

824

2S-S Seated Beam Connections

824

2S-6 Dimensioning

824

Bills of Material

Sheet-Metal Development
Straight-Line Development

826

23-2 The Packaging Industry

827

912

828

Chapter

26

Jigs and Fixtures 919

23-S Radial Line Development of Conical
Surfaces 834

26-1 Jig and Fixture Design

23-6 Development of Transition Pieces
by Triangulation 836

Jigs 919
Drill Jigs 921

23-7 Development of a Sphere

Drill Bushings

839

Jig Body

843

919

921

26-2 Drill Jig Components

23-8 Intersection of Flat Surfaces-Lines
Perpendicular 840

23-10 Intersecting Prisms · 844

909
910

Review and Assignments

23-4 Parallel Line Development of Cylindrical
Surfaces 831

23-9 Intersection of Cylindrical Surfaces

907

Calculations of Weights (Masses)

23-3 Radial Line Development of Flat Surfaces

87S

880

Structural Drafting".'887

810

Straight-Line Mechanism

PART

868

869

Review and Assignments

Locus of a Point 810
Cams versus Linkages

22-7 Ratchet Wheels

24-1 Pipes

Pipe Joints and Fitting

806

22-S Indexing

24

Valves

22-3 Positive-Motion Cams
22-4 Drum Cams

8S3

Pipe Drawings 867

Simplified Method for Laying Out Cam Motion

22-2 Plate Cams

847

923

923

Cap Screws and Dowel Pins
Locating Devices 924
Clamping Devices 926

923

911

905


xi

Contents

Locking Pins

927

Miscellaneous Standard Parts

27-2 Schematic Diagrams 942

Laying Out a Schematic Diagram

927

Design Examples 927

Graphic Symbols

26-3 Dimensioning Jig Drawings

27-3 Wiring (Connection) Diagrams 945
Basic Rules for Laying Out a Wiring Diagram

929

26-4 Fixtures 930
Milling Fixtures 930
Fixture Components 931
Fixture Design Considerations
Review and Assignments

27-4 Printed Circuit Boards 947
CAD for Printed Circuit Boards 949
Basic Rules for Laying Out a Printed Circuit

932

Sequence in Laying Out a Fixture

942

942

935

936

27 \l'"lll'~-------·
Electrical and Electronics Drawings 940

27-5 Block and Logic Diagrams
Block Diagrams 951
Logic Diagrams 952
Graphic Symbols 952
Review and Assignments

947

951

951

956

Chapter

27-1 Electrical and Electronics Drawings
Standardization 940
Using CAD for Electrical Drawings 941

940

Glossary

G-1

Appendix-Standard Parts and Technical Data
Index

1-1

A-1


Preface
Engineering Drawing and Design, Seventh Edition, prepares
students for drafting careers in modem, technology-intensive
industries. Technical drafting, like all technical areas, is
constantly changing; the computer has revolutionized the
way in which drawings and parts are made. This new edition
translates the most current technical information available
into the most useful for both instructor and student. The book
covers graphic communication, CAD, functional drafting,
material representation, shop processes, geometric tolerancing, true positioning, numerical control, electronic drafting,
and metrication. The authors synthesize, simplify, and convert complex drafting standards and procedures into understandable instructional units.
Like previous editions, this one is at the cutting edge of
drafting and computer technologies. Because board-drafting
skills are rapidly being replaced by computer-aided drafting
(CAD), this edition provides an enhanced view of CAD
while adhering to current ASME, ANSI, CSA, and ISO standards. Drafters must be knowledgeable about CAD and about

international standards, for design files can now be electronically transmitted across borders, or around the world.
The reader will find that this book helps build basic
skills. It also supplies the technical knowledge required in
today's marketplace.

TEXT FEATURES
• Knowing and Applying Drawing Standards. A drawing made in the United States must meet the requirements
set out in various ASME drawing standards publications.
Also, if a firm is involved in international marketing and
manufacturing, ISO guidelines (or other standards, such
as Canadian drawing standards) must be strictly followed. Drafters will be pleased to see that this book not
only covers these standards but also shows how to interpret and apply them. For example, the coverage of geometric tolerancing and true position is more comprehensive than in any other drafting text on the market
today.
• Knowing Manufacturing Materials and Their
Processes. The authors bring together and explain the
manufacturing materials that are available for engineering design. They describe the manufacturing processes
that influence the shape, appearance, and design of the
product.
xii

• Knowing Fastening Methods. The correct fastening
device plays a very important role in the cost, design,
and appearance of a product. Readers can learn about
various types of fasteners, both permanent and removable, that are currently available.
• Providing All the Necessary Information to Complete
the Design. The numerous assignments help the reader
gain practice. These assignments can be completed with
the help of a variety of Appendix tables reflecting realworld applications.
• Unit Approach in Teaching the Subject Matter. The
text's unit approach makes it possible for instructors to

put together a customized program of instruction that
suits the needs of their students and local industry.

KEY FEATURES OF THE
SEVENTH EDITION
Many users of the text were consulted before this new edition was undertaken. In response to their suggestions and
recommendations, we have made major changes and added
new features to this Seventh Edition, including:
• The four-color format is easy to read. Color has been
used as well to strengthen the important features in the
3000 line drawings and photographs.
• Chapter 2 explains how drawings are produced by computers and peripherals. Computers and the Internet Web
have become not only a laboratory but also a limit- less
technical resource and design facility.
• Solid modeling continues to play an important role in
Chap. 15. The power of personal computers and workstations brings 3-D modeling into the classroom, home,
CAD office, and on-site manufacturing centers.
• Chapter 16 contains more information on geometric
tolerancing and guidance on how to apply it to various
drawings. The chapter is up to date with ASME
standards and is more understandable to beginning
students.
• Chapter 19 covers concurrent engineering and project
modeling. Today, engineers and technicians work side
by side. All team members are responsible for coordinating efforts to deliver on-time and on-budget finished
products.


Preface

• The section on stamping in Chap. 23 it covers the process of forming and cutting thicker-gage metals that are
used in manufacturing.
• Chapter 27, on electronic drafting, is consistent with
solid-state, printed circuit board technology.
• Many chapters include new CAD features. They give
students and instructors a clear picture of how CAD can
be used in the classroom while maintaining a focus on
basic drafting principles. Many CAD features include
assignments.
• We have continued to provide the unit approach to
teaching, which divides chapters into "mini" teaching
units. Instructors find this approach to be a real bonus.
By choosing the appropriate units, instructors can put
together a customized program that suits the needs of
their students and local industry.
• Design concepts are covered in the text through drawing practice. Graduates find that these concepts give
them an excellent background in drafting and design.
Instructors can choose the units appropriate for their
program.
• This text continues to provide the latest drawing standards, indispensable to instructors. Current ANSI/ASME
and ISO drawing practices are examined better here than
in any other text.
• Numerous Internet assignments appear throughout the
book. The Websites, which relate directly to the topic
of the unit, are of companies students might select to
survey possible career opportunities. Instructors can
ask students to describe what they found at the sites
or to discuss sites that have the greatest regional career
interest. Students can also view various technical
product lines.

Each chapter begins with objectives and ends with
a chapter summary and list of key terms (both referenced
to chapter units) and draftinvg assignments. A Glossary,

xiii

precedes the Appendix. The four-color design highlights the
text's special features. Color is used to enhance the instructional value of the material. Thus, technical material is
appealing visually and easy to follow and understand.

ADDITIONAL RESOURCES
We have revised, improved, and added to the program's
ancillary products. Here is what's new and updated:

Drawing Workbook
The Workbook for Engineering Drawing and Design, Seventh Edition, covers all 27 chapters. It contains worksheets
that provide a partially completed solution for assignments
for each unit of the text. Each worksheet is referenced to a
specific chapter and unit number in the text. Instructions are
provided that give an overview for each assignment and references it to the appropriate text unit. The drawing problems
contain both U.S. customary (decimal inch) and metric (millimeter) units of measurement. The worksheets are perforated
for easy removal. Solutions are available to instructors at the
book's website at www.mhhe.com/jensen.

Additional Chapters on Advanced Topics
Three additional chapters, covering advanced topics, are provided on the book's website:
Chapter 28-Applied Mechanics
Chapter 29-Strength of Materials
Chapter 30-Fluid Power
Comments and suggestions concerning this and future

editions of the text are most welcome.
Visit the text website at: www.mhhe.com/jensen for various
resources available to instructors and students.


Acknowledgments
The authors are indebted to the members of ASME
Y14.5M-1994 (R2004), Dimensioning and Tolerancing, and
the members of the CAN/CSA-B78.2-M91, Dimensioning
and Tolerancing of Technical Drawings, for the countless
hours they have contributed to making successful standards.
The authors and staff of McGraw-Hill wish to express
their appreciation to the following individuals for their
responses to questionnaires and their professional reviews of
the new edition:

xiv

Fred Brasfield
Tarrant County College
Ralph Dirksen
Western Illinois University
James Freygang
Ivy Tech Community College
George Gibson
Athens Technical College
James Haick
Columbus Technical College
Richard Jerz
St. Ambrose University

Bisi Oluyemi
Morehouse College
Robert A. Osnes
Everett Community College
Douglas L. Ramers
University of Evansville
Jeff Raquet
University of North Carolina-Charlotte
Larry Shacklett
Southeastern Community College
Warner Smidt
University of Wisconsin-Platteville
James Stokes
Ivy Tech Community College of Indiana
Slobodan Urdarevik
Western Michigan University
Dean Zirwas
Indian River Community College


About the Authors
Cecil H. Jensen
Cecil H. Jensen authored or coauthored many successful
technical books, including Engineering Drawing and
Design, Fundamentals of Engineering Drawing, FundamentaL~ of Engineering Graphics (formerly called Drafting Fundamentals), Interpreting Engineering Drawings,
Geometric Dimensioning and Tolerancing for Engineering
and Manufacturing Technology, Architectural Drawing
and Design for Residential Construction, Home Planning
and Design, and Interior Design. Some of these books

were printed in three languages and are popular in many
countries.
Mr. Jensen was a member of the Canadian Standards
Committee (CSA) on Technical Drawings (which includes
both mechanical and architectural drawing) and headed the
Committee on Dimensioning and Tolerancing. He was Canada's
ANSI representative. He represented Canada at two world ISO
conferences in Oslo and Paris on the standardization of technical drawings. Cecil Jensen passed away in April, 2005.

Jay D. Helsel
Jay D. Helsel is professor emeritus of applied engineering
and technology at California University of Pennsylvania. He
earned the master's degree from Pennsylvania State University
and a doctoral degree in educational communications and
technology from the University of Pittsburgh. He holds a
certificate in airbrush techniques and technical illustration
from the Pittsburgh Art Institute. He has worked in industry
and has also taught drafting, metalworking, woodworking,

and a variety of laboratory and professional courses at both
the secondary and the college levels.
Dr. Helsel is now a full-time writer. He coauthored
Engineering Drawing and Design, Fundamentals of Engineering Drawing, Programmed Blueprint Reading, the popular
high school drafting textbook Mechanical Drawing: Board
and CAD Techniques, now in its thirteenth edition, and
Interpreting Engineering Drawings.

Dennis R. Short
Dennis R. Short is professor of computer graphics technology at the School of Technology, Purdue University. He
completed his undergraduate and graduate work at Purdue

University and also studied at the University of Maryland,
College Park. He enjoys teaching traditional engineering
design and drafting, computer-aided drafting and design,
computer-integrated manufacturing (CIM), and advanced
modeling and animation. While at Purdue, he implemented

the first instructional CAD system for the School of Technology, as well as the first networked PC-based CAD laboratory. In addition to teaching undergraduates, he is on the
graduate faculty. He codirects the Purdue International Center for Entertainment Technology (PICET), a university-level
interdisciplinary research and development center. Dr. Short
prepared the Instructor Wraparound Edition for Engineering
Drawing and Design, Fifth and Sixth Editions.

XV



BASIC DRA:

Chapter 1 Engineering
Chapter 2

Computer-

Chapter 3
Chapter 4
Chapter 5
Chapter 6 Theory of Shape
Chapter 7

Auxiliary Views and

Chapter 8 Basic Dimensioning
Chapter 9

Sections

235


Chapter

1

Engineering Graphics
as a Language
OBJECTIVES
After studying this chapter, you will be able to:

• Define common terms used in drawing and design. ( 1-1)
• Describe drawing standards and the standards organizations. (1-1)
• Understand the training and qualifications needed for careers in drawing
and design. (1-2)
• Understand the uses of CAD in the drafting office. (1-3)
• Describe drafting equipment such as drafting machines, slides, triangles,
scales, and compasses. (1-4)
• Use pencils and erasers in drafting. (1-4)

1-1

THE LANGUAGE OF INDUSTRY

Since earliest times people have used drawings to communicate and record ideas
so that they would not be forgotten. Graphic representation means dealing
with the expression of ideas by lines or marks impressed on a surface. A drawing
is a graphic representation of a real thing. Drafting, therefore, is a graphic
language, because it uses pictures to communicate thoughts and ideas. Because
these pictures are understood by people of different nations, drafting is referred
to as a universal language.
Drawing has developed along two distinct lines, with each form having a
different purpose. On the one hand artistic drawing is concerned mainly with
the expression of real or imagined ideas of a cultural nature. Technical drawing,
on the other hand, is concerned with the expression of technical ideas or ideas
of a practical nature, and it is the communication method used in all branches
of technical industry.
Even highly developed word languages are inadequate for describing the
size, shape, texture and relationship of physical objects. For every manufactured
object there are drawings that describe its physical shape and size completely
and accurately, communicating engineering concepts to manufacturing. For this
reason, drafting is called the language of industry.
Drafters translate the ideas, rough sketches, specifications, and calculations
of engineers, architects, and designers into working plans that are used in making
a product (Table 1-1). Drafters calculate the strength, reliability, and cost of
materials. In their drawings and specifications, they describe exactly what materials workers are to use on a particular job. To prepare their drawings, drafters


CHAPTER 1

TABLE 1-1

Engineering Graphics as a Language

Various fields of drafting.

Mechanical

Designing
Testing
Manufacturing
Maintenance
Construction

Materials
Machines
Devices

Power generation
Transportation
Manufacturing
Power services
Atomic energy
Marine vessels

Architectural

Planning
Designing
Supervising

Buildings
Environment

Landscape

Commercial buildings
Residential buildings
Institutional buildings
Environmental space forms

Electrical

Designing
Developing
Supervising
Programming

Computers
Electronics
Power
Electrical

Power generation
Power application
Transportation
Illumination
Industrial electronics
Communications
Instrumentation
Military electronics

Aerospace

Planning
Designing
Testing

Missiles
Planes
Satellites
Rockets

Aerodynamics
Structural design
Instrumentation
Propulsion systems
Materials
Reliability testing
Production methods

Piping

Designing
Testing
Manufacturing
Maintenance
Construction

Buildings
Hydraulics
Pneumatics
Pipe lines

Liquid transportation
Manufacturing
Power services
Hydraulics
Pneumatics

,J5
4

"

R,
100 n
20W

3

Structural designs
:Buildings
Planes
Ships
Automobiles
Bridges

Planning
Designing
Manufacturing
Construction

Technical illustration

Promotion
Designing
Illustrating

Catalogs
Magazines
Displays

New products
Assembly instructions
Presentations
community projects
Renewal programs

3


4

PART 1 Basic Drawing and Design

use either computer-aided drawing and design (CAD) systems or board drafting instruments, such as compasses, protractors, templates, and triangles, as well as drafting machines
that combine the functions of several devices. They also may
use engineering handbooks, tables, and calculators to assist
in solving technical problems.
Drafters are often classified according to their type of
work or their level of responsibility. Senior drafters (designers)
use the preliminary information provided by engineers and
architects to prepare design layouts (drawings made to scale

of the object to be built). Detailers Gunior drafters) make
drawings of each part shown on the layout, giving dimensions, material, and any other information necessary to make
the detailed drawing clear and complete. Checkers carefully
examine drawings for errors in computing or recording sizes
and specifications.
Drafters may also specialize in a particular area, such as
mechanical, electrical, electronic, aeronautic, structural, piping, or architectural drafting.

Drawing Standards
Throughout the long history of drafting, many drawing conventions, terms, abbreviations, and practices have come into
common use. It is essential that different drafters use the
same practices if drafting is to serve as a reliable means of
communicating technical theories and ideas.
In the interest of worldwide communication, the International Organization of Standardization (ISO) was established in 1946. One of its committees, ISO TCIO, was
formed to deal with the subject of technical drawings. Its
goal was to develop a universally accepted set of drawing
standards. Today most countries have adopted, either in full
or with minor changes, the standards established by this
committee, making drafting a truly universal language.
The American Society of Mechanical Engineers (ASME)
is the governing body that establishes the standards for the
United States through its ASME Y14.5 committee (ANSI),
made up of selected personnel from industry, technical organizations, and education. Members from the ASME Yl4.5
also serve on the ISO TCIO subcommittee.
The standards used throughout this text reflect the current
thinking of the ASME standards committee. These standards
apply primarily to end-product drawings. End-product drawings usually consist of detail or part drawings and assembly
or subassembly drawings, and are not intended to fully cover
other supplementary drawings, such as checklists, item lists,
schematic diagrams, electrical wiring diagrams, flowcharts,

installation drawings, process drawings, architectural drawings, and pictorial drawings.
The information and illustrations presented here have
been revised to reflect current industrial practices in the
preparation and handling of engineering documents. The
increased use of reduced-size copies of engineering drawings made from microfilm and the reading of microfilm
require the proper preparation of the original engineering

document regardless of whether the drawing was made
manually or by computer (CAD). All future drawings
should be prepared for eventual photographic reduction or
reproduction. The observance of the drafting practices
described in this text will contribute substantially to the
improved quality of photographically reproduced engineering
drawings.

INTERNET CONNECTION Visit this site and report on
careers in drafting and related technical fields:
www.bls.gov/bls/occupation

1-2

CAREERS IN
ENGINEERING GRAPHICS

The Student
While students are learning basic drafting skills, they will also
be increasing their general technical knowledge, learning
about some of the enginering and manufacturing processes
involved in production. Not all students will choose a drafting
career. However, an understanding of this graphic language is

necessary for anyone who works in any of the fields of technology, and is essential for those who plan to enter the skilled
trades or become a technician, technologist, or engineer.
Because a drawing is a set of instructions that the worker
will follow, it must be accurate, clean, correct, and complete.
When drawings are made with the use of instruments, they
are called instrument (or board) drawings. When they are
developed with the use of a computer, they are known as
computer-aided drawings. When made without instruments
or the aid of a computer, drawings are referred to as sketches.
The ability to sketch ideas and designs and to produce accurate drawings is a basic part of drafting skills.
In everyday life, a knowledge of technical drawings is
helpful in understanding house plans and assembly, maintenance, and operating instructions for many manufactured or
hobby products.

Places of Employment
There are well over 300,000 people working in CAD or
drafting positions in the United States. A significant number
of them are women. About 9 out of 10 drafters are employed
in private industry. Manufacturing industries that employ a
large number of drafters are those making machinery, electrical equipment, transportation equipment, and fabricated metal
products. Nonmanufacturing industries employing a large
number of drafters are engineering and architectural consulting
firms, construction companies, and public utilities.
Drafters also work for the government; the majority work
for the armed services. Drafters employed by state and local
governments work chiefly for highway and public works


CHAPTER 1 Engineering Graphics as a Language

departments. Several thousand drafters are employed by
colleges and universities and by other nonprofit organizations.

Training, Qualifications, and Advancement
Many design careers are available at different technical levels
of performance. Most companies are in need of design and
drafting services for growth in technical development, construction, or production. Any person interested in becoming
a drafter can acquire the necessary training from a number
of sources, including junior and community colleges, extension divisions of universities, vocational/technical schools,
and correspondence schools. Others may qualify for drafting
positions through on-the-job training programs combined
with part-time schooling.
The prospective drafter's training in post-high school
drafting programs should include courses in mathematics
and physical sciences, as well as in CAD and CADD. Studying
fabrication practices and learning some trade skills are
also helpful, since many higher-level drafting jobs require
knowledge of manufacturing or construction methods. This
is especially true in the mechanical discipline because of the
implementation of CAD/CAM (computer-aided drawing/
computer-aided manufacturing). Many technical schools
offer courses in structural design, strength of materials,
physical metallurgy, CAM, and robotics.
As drafters gain skill and experience, they may advance
to higher-level positions such as checkers, senior drafters,
designers, supervisors, and managers (Fig. 1-1). Drafters who
take additional courses in engineering and mathematics are
often able to qualify for engineering positions.
Qualifications for success as a drafter include the ability
to visualize objects in three dimensions and the development

of problem-solving design techniques. Since the drafter is the
one who finalizes the details on drawings, attentiveness to
detail is a valuable asset.

Employment Outlook
Employment opportunities for drafters are expected to remain
stable as a result of the complex design problems of modern

Fig. 1-1

Positions within the drafting office.

5

products and processes. The need for drafters will, however,
fluctuate with local and national economics. Since drafting
is a part of manufacturing, job opportunities in this field will
also rise or drop in accordance with various manufacturing
industries. The demand for drafters will be high in some
areas and low in others as a result of high-tech expansion or
a slump in sales. In addition, computerization is creating
many new products, and support and design occupations,
including drafters, will continue to grow. On the other hand,
photo-reproduction of drawings and expanding use of CAD
have eliminated many routine tasks done by drafters. This
development will probably reduce the need for some less
skilled drafters.
References and Source Materials
1. Charles Bruning Co.
2. Occupational Outlook Handbook.

INTERNET CONNECTION Visit this site to review information
on drafting certification, specific job openings, and
opportunities to post resumes: />
1-3

THE DRAFTING OFFICE

Drafting room technology has progressed at the same rapid
pace as the economy of the country. Many changes have
taken place in the modern drafting room compared to the
typical drafting room scene before CAD, as shown in Fig. 1-2,
p. 6. Not only is there far more equipment, but it is of much
higher quality. Noteworthy progress has been and continues
to be made.
The drafting office is the starting point for all engineering
work. Its product, the engineering drawing, is the main
method of communication among all people concerned with
the design and manufacture of parts. Therefore, the drafting
office must provide accommodations and equipment for the
drafters, from designer and checker to detailer or tracer; for
the personnel who make copies of the drawings and file the
originals; and for the secretarial staff who assist in the preparation of the drawings. Typical drafting workstations are
shown in Figs. 1-3 and 1-4, p. 6.
Fewer engineering departments now rely on board drafting methods. Computers are replacing drafting boards at a
steady pace because of increased productivity. However,
where a high volume of finished or repetitive work is not
necessary, board drafting does the job adequately. CAD and
board drafting can serve as full partners in the design process,
enabling the designer to do jobs that are simply not possible

or feasible with board equipment alone.
Besides increasing the speed with which a job is done,
a CAD system can perform many of the tedious and repetitive


6

PART 1

Basic Drawing and Design

(A) THE DRAFTING OFFICE AT THE TURN OF THE CENTURY.

Fig. 1-3

Board drafting office.

(B) BOARD DRAFTING OFFICE UP TO 1970.

Fig. 1-4 CAD drafting office.

(C) TODAY'S DRAFTING OFFICE.

Fig. 1-2

Evolution of the drafting office.

tasks ordinarily required of a drafter, such as lettering and
differentiating line weights. CAD thus frees the drafter to be
more creative while it quickly performs the mundane tasks

of drafting. It is estimated that CAD has been responsible

for an improvement of at least 30 percent in production in
terms of time spent on drawing.
A CAD system by itself cannot create. A drafter must
create the drawing, and thus a strong design and drafting
background remains essential.
It may not be practical to handle all the workload in a
design or drafting office on a CAD system. Although most
design and drafting work certainly can benefit from it, some
functions will continue to be done by traditional means.
Thus some companies use CAD for only a portion of the
workload. Others use CAD almost exclusively. Whatever
the percentage of CAD use, one fact is certain: It has had,
and will continue to have, a dramatic effect on design and
drafting careers.
Once a CAD system has been installed, the required
personnel must be hired or trained. Trained personnel generally originate from one of three popular sources: educational
institutions, CAD equipment manufacturer training courses,
and individual company programs.


CHAPTER 1

Engineering Graphics as a Language

7

INTERNET CONNECTION Visit the following site for
information on computers and related accessories for

the drafting office: />Examine this site and report on the typical furniture
and equipment needed when planning a new drafting
office: />Obtain information on the latest printers, scanners, and
copiers: />
1-4

BOARD DRAFTING

Over the years, the designer's chair and drafting table have
evolved into a drafting station that provides a comfortable,
integrated work area. Yet much of the equipment and supplies employed years ago are still in use today, although
vastly improved.

Special tables and desks are manufactured for use in singlestation or multistation design offices. Typical are desks with
attached drafting boards. The boards may be used by the
occupant of the desk to which it is attached, in which case
it may swing out of the way when not in use, or may be
reversed for use by the person in the adjoining station.
In addition to such special workstations, a variety of
individual desks, chairs, tracing tables, filing cabinets, and
special storage devices for equipment are available.
The drawing sheet is attached directly to the surface of
a drafting table (Fig. 1-5). Most professional drafting tables

STEEL DRAFTING TABLE

ELECTRIC DRAFTING TABLE

Fig. 1-5

Drafting tables.

Board drafting equipment.

have a special overlay drawing surface material that "recovers"
from minor pinholes and dents.

Drafting Furniture

WOOD DRAFTING TABLE

Fig. 1-6

Drafting Equipment
See Fig. 1-6 for a variety of drafting equipment.

Drafting Machines
In a manually equipped drafting office, where the designer
is expected to do accurate drafting, a drafting machine,
or parallel slide, is used. A drafting machine, which is
attached to the top of the table, combines the functions of
a parallel slide, triangles, scale, and protractor and is
estimated to save up to 50 percent of the user's time. All
positioning is done with one hand, and the other hand is
free to draw.
Two types are currently available (Fig. 1-7, p. 8). In the
track type, a vertical beam carrying the drafting instruments
rides along a horizontal beam fastened to the top of the table.
In the arm (or elbow) type, two arms pivot from the top of
the machine and are relative to each other.

The track-type machine has several advantages over the
arm type. It is better suited for large drawings and is normally more stable and accurate. The track type also allows
the drafting table to be positioned at a steeper angle and permits locking in the vertical and horizontal positions.
Some track-type drafting machines provide a digital display of angles, the X- Y coordinates, and a memory function.

Parallel Slide
The parallel slide, also called the parallel bar, is used in
drawing horizontal lines and for supporting triangles when
vertical and sloping lines are being drawn (Fig. 1-8, p. 8).
It is fastened on each end to cords, which pass over pulleys. This arrangement permits movement up and down the


8

PART 1

Basic Drawing and Design

Fig. 1-8 Drafting table with parallel slide.

45° triangles. Singly or in combination, these triangles can
be used to form angles in multiples of 15°. For other angles,
the adjustable triangle (Fig. 1-11) is used (p. 10).

Scales
Scale may refer to the measuring instrument or the size to
which a drawing is to be made.
(A) TRACK TYPE

(B)ARMTVPE

Fig. 1-7

Drafting machines.

board while maintaining the parallel slide in a horizontal
position.

Triangles
Triangles are used together with the parallel slide when
you are drawing vertical and sloping lines (Fig. 1-9). The
triangles most commonly used are the 30/60° and the

Shown in Fig. 1-10, p. 10, are the
common shapes of scales used by drafters to make measurements on their drawings. Scales are used only for measuring
and are not to be used as a straightedge for drawing lines. It
is important that drafters draw accurately to scale. The scale
to which the drawing is made must be given in the title
block or strip that is part of the drawing.
Measuring Instrument

Sizes to Which Drawings Are Made When an object is
drawn at its actual size, the drawing is called full scale
or scale 1:1. Many objects, however, such as buildings,
ships, or airplanes, are too large to be drawn full scale,
so they must be drawn to a reduced scale. An example
would be the drawing of a house to a scale of 1,4 in. = 1 ft
or 1:48.
Frequently, objects such as small wristwatch parts are
drawn larger than their actual size so that their shape can be

seen clearly and dimensioned. Such a drawing has been
drawn to an enlarged scale. The minute hand of a wristwatch,
for example, could be drawn to a scale of 5:1.
Many mechanical parts are drawn to half scale, 1:2,
and quarter scale, 1:4, or nearest metric scale, 1:5. The
scale to which the part is drawn and the actual size of the
part are shown as an equation, the drawing scale shown
first. With reference to the 1:5 scale, the left side of the equation represents a unit of the size drawn; the right side represents the equivalent 5 units of measurement of the actual
object.
Scales are made with a variety of combined scales
marked on their surfaces. This combination of scales spares
the drafter the necessity of calculating the sizes to be drawn
when working to a scale other than full size.


CHAPTER 1

Engineering Graphics as a Language

9

(A) THE 45° TRIANGLE

(B) THE 60° TRIANGLE

(C) THE TRIANGLES IN COMBINATION

Fig. 1-9

Triangles.

Metric Scales The linear unit of measurement for mechanical drawings is the millimeter. Scale multipliers and divisors
of 2 and 5 are recommended (Fig. 1-12, p. 10).
The units of measurement for architectural drawings are
the meter and millimeter. The same scale multipliers and
divisors used for mechanical drawings are used for architectural drawings.

The divisions, or parts of an inch, can be used to represent
feet, yards, rods, or miles. This scale is also useful in
mechanical drawing when the drafter is dealing with decimal dimensions.
On fractional inch scales, multipliers or divisors of 2, 4,
8, and 16 are used, offering such scales as full size, half size,
and quarter size.

Inch (U.S. Customary) Scales

Foot Scales These scales are used mostly in architectural
work (Fig. 1-14, p. 11). They differ from the inch scales in
that each major division represents a foot, not an inch, and
end units are subdivided into inches or parts of an inch. The
more common scales are Ys in. = 1 ft, Y. in. = 1 ft, 1 in. =
1 ft, and 3 in. = 1 ft. The most commonly used inch and
foot scales are shown in Table 1-2, p. 12.

There are three types of scales that show various values that are equal to 1 inch (in.) (Fig. 1-13, p. 11 ).
They are the decimal inch scale, the fractional inch scale,
and the scale that has divisions of 10, 20, 30, 40, 50, 60,
and 80 parts to the inch. The last scale is known as the civil
engineer's scale. It is used for making maps and charts.
Inch Scales

10

PART 1

Basic Drawing and Design

REGULAR

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20

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Fig. 1-10

1000
500
200
100
50
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Drafting scales.
Fig. 1-12

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1000

Metric scales.

Compasses

The compass is used for drawing circles and arcs. Several
basic types and sizes are available (Fig. 1-15, p. 12).

Fig. 1-11

Adjustable triangle.

• Friction head compass, standard in most drafting sets.
• Bow compass, which operates on the jackscrew or ratchet
principle by turning a large knurled nut.
• Drop bow compass, used mostly for drawing small circles. The center rod contains the needle point and remains
stationary while the pencil leg revolves around it.
• Beam compass, a bar with an adjustable needle and penciland-pen attachment for drawing large arcs or circles.