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Machine Drawing and Drafting

Engineering Drawings and Drafting Guide Resources

Machine Drawing and Drafting
K.L. Narayana
P. Kannaiah
K. Venkata Reddy
474 Pages

Open: Machine Drawing and Drafting
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Introduction

A technical person can use the graphic language as powerful means of communication with others for conveying ideas on technical matters. However, for effective exchange of ideas with others, the engineer must have proficiency in (i) language, both written and oral, (ii) symbols associated with basic sciences and (iii) the graphic language. Engineering drawing is a suitable graphic language from which any trained person can visualise the required object. As an engineering drawing displays the exact picture of an object, it obviously conveys the same ideas to every trained eye.

Irrespective of language barriers, the drawings can be effectively used in other countries, in addition to the country where they are prepared. Thus, the engineering drawing is the universal language of all engineers.

Engineering drawing has its origin sometime in 500 BC in the regime of King Pharos of Egypt when symbols were used to convey the ideas among people.

TOC

Introduction
1.1 Graphic Language 1
1.1.1 General 1
1.1.2 Importance of Graphic Language 1
1.1.3 Need for Correct Drawings 1
1.2 Classification of Drawings 2
1.2.1 Machine Drawing 2
1.2.2 Production Drawing 2
1.2.3 Part Drawing 2
1.2.4 Assembly Drawing 3

 Principles of Drawing
2.1 Introduction 10
2.2 Drawing Sheet 10
2.2.1 Sheet Sizes 10
2.2.2 Designation of Sizes 10
2.2.3 Title Block 11
2.2.4 Borders and Frames 11
2.2.5 Centring Marks 12
2.2.6 Metric Reference Graduation 12
2.2.7 Grid Reference System (Zoning) 13
2.2.8 Trimming Marks 13
2.3 Scales 13
2.3.1 Designation 13
2.3.2 Recommended Scales 13
2.3.3 Scale Specification 13
2.4 Lines 14
2.4.1 Thickness of Lines 15
2.4.2 Order of Priority of Coinciding Lines 16
2.4.3 Termination of Leader Lines 17
2.5 Lettering 18
2.5.1 Dimensions 18
2.6 Sections 19
2.6.1 Hatching of Sections 20
2.6.2 Cutting Planes 21
2.6.3 Revolved or Removed Section 23
2.6.4 Half Section 24
2.6.5 Local Section 24
2.6.6 Arrangement of Successive Sections 24
2.7 Conventional Representation 24
2.7.1 Materials 24
2.7.2 Machine Components 24
2.8 Dimensioning 25
2.8.1 General Principles 25
2.8.2 Method of Execution 28
2.8.3 Termination and Origin Indication 30
2.8.4 Methods of Indicating Dimensions 30
2.8.5 Arrangement of Dimensions 32
2.8.6 Special Indications 33
2.9 Standard Abbreviations 37
2.10 Examples 38

Orthographic Projections
3.1 Introduction 43
3.2 Principle of First Angle Projection 43
3.3 Methods of Obtaining Orthographic Views 44
3.3.1 View from the Front 44
3.3.2 View from Above 44
3.3.3 View from the Side 44
3.4 Presentation of Views 45
3.5 Designation and Relative Positions of Views 45
3.6 Position of the Object 46
3.6.1 Hidden Lines 47
3.6.2 Curved Surfaces 47
3.7 Selection of Views 47
3.7.1 One-view Drawings 48
3.7.2 Two-view Drawings 48
3.7.3 Three-view Drawings 49
3.8 Development of Missing Views 50
3.8.1 To Construct the View from the Left, from the Two Given Views 50
3.9 Spacing the Views 50
3.10 Examples 51

Sectional Views
4.1 Introduction 64
4.2 Full Section 64
4.3 Half Section 65
4.4 Auxiliary Sections 66
4.5 Examples 67

Screwed Fasteners
5.1 Introduction 77
5.2 Screw Thread Nomenclature 77
5.3 Forms of Threads 78
5.3.1 Other Thread Profiles 79
5.4 Thread Series 80
5.5 Thread Designation 81
5.6 Multi-start Threads 81
5.7 Right Hand and Left Hand Threads 81
5.7.1 Coupler-nut 82
5.8 Representation of Threads 82
5.8.1 Representation of Threaded Parts in Assembly 84
5.9 Bolted Joint 85
5.9.1 Methods of Drawing Hexagonal (Bolt Head) Nut 85
5.9.2 Method of Drawing Square (Bolt Head) Nut 87
5.9.3 Hexagonal and Square Headed Bolts 88
5.9.4 Washers 89
5.9.5 Other Forms of Bolts 89
5.9.6 Other Forms of Nuts 91
5.9.7 Cap Screws and Machine Screws 92
5.9.8 Set Screws 93
5.10 Locking Arrangements for Nuts 94
5.10.1 Lock Nut 94
5.10.2 Locking by Split Pin 95
5.10.3 Locking by Castle Nut 95
5.10.4 Wile’s Lock Nut 96
5.10.5 Locking by Set Screw 96
5.10.6 Grooved Nut 96
5.10.7 Locking by Screw 96
5.10.8 Locking by Plate 97
5.10.9 Locking by Spring Washer 97
5.11 Foundation Bolts 98
5.11.1 Eye Foundation Bolt 98
5.11.2 Bent Foundation Bolt 98
5.11.3 Rag Foundation Bolt 98
5.11.4 Lewis Foundation Bolt 99
5.11.5 Cotter Foundation Bolt 100

Key, Cotters and Pin Joints
6.1 Introduction 103
6.2 Keys 103
6.2.1 Saddle Keys 103
6.2.2 Sunk Keys 104
6.3 Cotter Joints 109
6.3.1 Cotter Joint with Sleev 111
6.3.2 Cotter Joint with Socket and Spigot Ends 111
6.3.3 Cotter Joint with a Gib 111
6.4 Pin Joints 112
6.4.1 Knuckle Joint 113

Shaft Coupling
7.1 Introduction 115
7.2 Rigid Couplings 115
7.2.1 Sleeve or Muff Couplings 115
7.2.2 Flanged Couplings 117
7.3 Flexible Couplings 119
7.3.1 Bushed Pin Type Flanged Coupling 119
7.3.2 Compression Coupling 120
7.4 Dis-engaging Couplings 120
7.4.1 Claw Coupling 120
7.4.2 Cone Coupling 122
7.5 Non-aligned Couplings 123
7.5.1 Universal Coupling (Hooke’s Joint) 123
7.5.2 Oldham Coupling 124
7.5.3 Cushion Coupling 125

Pipe Joints
8.1 Introduction 127
8.2 Joints for Steam Pipes 127
8.2.1 Joints for Cast Iron Pipes 128
8.2.2 Joints for Copper Pipes 129
8.2.3 Joints for Wrought Iron and Steel Pipes 130
8.3 Joints for Hydraulic Pipes 130
8.3.1 Socket and Spigot Joint 131
8.3.2 Flanged Joint 131
8.4 Special Pipe Joints 131
8.4.1 Union Joint 131
8.4.2 Expansion Joint 133
8.5 Pipe Fittings 134
8.5.1 GI Pipe Fittings 135
8.5.2 CI Pipe Fittings 136
8.5.3 PVC Pipes and Fittings 136
8.6 Pipe Layout 140

Pulleys
9.1 Introduction 142
9.2 Belt Driven Pulleys 142
9.2.1 Flat Belt Pulleys 142
9.2.2 V-belt Pulleys 145
9.2.3 Rope Pulley 147

Riveted Joints
10.2 Rivets and Riveting 150
10.2.1 Rivet 150
10.2.2 Riveting 150
10.2.3 Caulking and Fullering 151
10.3 Rivet Heads 151
10.4 Definitions 151
10.4.1 Pitch 151
10.4.2 Margin 152
10.4.3 Chain Riveting 152
10.4.4 Zig-Zag Riveting 152
10.4.5 Row Pitch 152
10.4.6 Diagonal Pitch 152
10.5 Classification of Riveted Joints 152
10.5.1 Structural Joints 152
10.5.2 Boiler Joints 154

Welded Joints
11.1 Introduction 161
11.2 Welded Joints and Symbols 161
11.2.1 Position of the Weld Symbols on the Drawings 162
11.2.2 Conventional Signs 166
11.2.3 Location of Welds 166
11.2.4 Position of the Arrow Line 166
11.2.5 Position of the Reference Line 167
11.2.6 Position of the Symbol 167
11.3 Dimensioning of Welds 168
11.3.1 Dimensioning Fillet Welds 168
11.4 Edge Preparation of Welds 168
11.5 Surface Finish 169
11.6 Rules to be Observed while Applying Symbols 169
11.7 Welding Process Designations (Abbreviations) 171
11.8 Examples 171

Bearings
12.1 Introduction 176
12.2 Sliding Contact Bearings 176
12.2.1 Journal Bearings 176
12.3 Rolling Contact (Anti-friction) Bearings 183
12.3.1 Radial Bearings 184
12.3.2 Thrust Bearings 185

Chains and Gears
13.1 Introduction 189
13.2 Chain Drives 189
13.3 Roller Chains 189
13.4 Inverted Tooth or Silent Chains 190
13.5 Sprockets 190
13.6 Design of Roller Chain Drives 190
13.7 Gears 191
13.8 Types of Gears 191
13.9 Gear Nomenclature 191
13.10 Tooth Profiles 192
13.10.1 Involute Tooth Profile 192
13.10.2 Approximate Construction of Tooth Profiles 193
13.11 Gears and Gearing 195
13.11.1 Spur Gear 195
13.11.2 Spur Gearing 195
13.11.3 Helical Gear 196
13.11.4 Helical Gearing 196
13.11.5 Bevel Gear 196
13.11.6 Bevel Gearing 197
13.11.7 Worm and Worm Gear (Wheel) 197

Jig and Fixtures
14.1 Introduction 200
14.2 Presentation of Work Piece 200
14.3 Jig Components 200
14.3.1 Jig Body 200
14.3.2 Locating Devices 201
14.3.3 Clamping Devices 201
14.3.4 Bushings 201
14.4 Various Types of Jigs 203
14.4.1 Channel Jig 203
14.4.2 Box Jig 204
14.5. Fixture Components 204
14.5.1 Fixture Base 204
14.5.2 Clamps 204
14.5.3 Set Blocks 205
14.6 Types of Fixtures 205
14.6.1 Indexing Type Milling Fixture 205
14.6.2 Turning Fixture 205
14.6.3 Welding Fixture 206

Limits, Tolerances, and Fits
15.1 Introduction 208
15.2 Limit System 208
15.2.1 Tolerance 208
15.2.2 Limits 208
15.2.3 Deviation 208
15.2.4 Actual Deviation 208
15.2.5 Upper Deviation 208
15.2.6 Lower Deviation 209
15.2.7 Allowance 209
15.2.8 Basic Size 209
15.2.9 Design Size 209
15.2.10 Actual Size 209
15.3 Tolerances 209
15.3.1 Fundamental Tolerances 212
15.3.2 Fundamental Deviations 212
15.3.3 Method of Placing Limit Dimensions (Tolerancing Individual Dimensions) 225
15.4 Fits 227
15.4.1 Clearance Fit 227
15.4.2 Transition Fit 227
15.4.3 Interference Fit 228
15.5 Tolerances of Form and Position 232
15.5.1 Introduction 232
15.5.2 Form Variation 232
15.5.3 Position Variation 232
15.5.4 Geometrical Tolerance 232
15.5.5 Tolerance Zone 232
15.5.6 Definitions 232
15.5.7 Indicating Geometrical Tolerances on the Drawing 234
15.5.8 Indication of Feature Controlled 234
15.5.9 Standards Followed in Industry 235

Surface Roughness
16.1 Introduction 242
16.2 Surface Roughness 242
16.2.1 Actual Profile, Af 243
16.2.2 Reference Profile, Rf 243
16.2.3 Datum Profile, Df 243
16.2.4 Mean Profile, Mf 243
16.2.5 Peak-to-valley Height, Rt 243
16.2.6 Mean Roughness Index, Ra 243
16.2.7 Surface Roughness Number 243
16.3 Machining Symbols 245
16.4 Indication of Surface Roughness 245
16.4.1 Indication of Special Surface Roughness Characteristics 246
16.4.2 Indication of Machining Allowance 248
16.4.3 Indications of Surface Roughness Symbols on Drawings 248

Blueprint Reading
17.1 Introduction 251
17.2 Examples 251
17.2.1 Rear Tool Post 251
17.2.2 Pump Housing 252
17.2.3 Gear Box Cover 254
17.2.4 Steam Stop Valve 254
17.3 Exercises 257
17.3.1 Worm Gear Housing 257
17.3.2 Connector 258
17.3.3 Square Tool Post 259
17.3.4 Milling Fixture 261

Assembly Drawings
18.1 Introduction 264
18.2 Engine Parts 265
18.2.1 Stuffing Box 265
18.2.2 Steam Engine Crosshead 265
18.2.3 Crosshead 265
18.2.4 Steam Engine Connecting Rod End 265
18.2.5 Marine Engine Connecting Rod End 267
18.2.6 Piston 270
18.2.7 Radial Engine Sub-assembly 271
18.2.8 Eccentric 273
18.2.9 Rotary Gear Pump 273
18.2.10 Air Valve 276
18.2.11 Fuel Injector 276
18.2.12 Single Plate Clutch 276
18.2.13 Multiplate Friction Clutch 279
18.3 Machine Tool Parts and Accessories 284
18.3.1 Single Tool Post 284
18.3.2 Square Tool Post 284
18.3.3 Clapper Block 285
18.3.4 Shaper Tool Head Slide 287
18.3.5 Lathe Tail-stock 289
18.3.6 Milling Machine Tail-stock 289
18.3.7 Revolving Centre 291
18.3.8 Floating Reamer Holder 294
18.3.9 Machine Vice 294
18.3.10 Swivel Machine Vice 294
18.3.11 Drill Jig 298
18.3.12 Indexing Drill Jig 299
18.3.13 Self-centring Chuck 299
18.3.14 Four Jaw Chuck 299
18.4 Valves and Boiler Mountings 303
18.4.1 Gate Valve 303
18.4.2 Screw Down Stop Valve 306
18.4.3 Non-return Valve (Light Duty) 306
18.4.4 Non-return Valve 306
18.4.5 Air Cock 310
18.4.6 Blow-off Cock 310
18.4.7 Feed Check Valve 310
18.4.8 Pressure Relief Valve 314
18.4.9 Lever Safety Valve 315
18.4.10 Spring Loaded Relief Valve 318
18.4.11 Ramsbottom Safety Valve 318
18.5 Miscellaneous Parts 321
18.5.1 Socket and Spigot Joint 321
18.5.2 Knuckle Joint 322
18.5.3 Protected Flanged Coupling 323
18.5.4 Bushed-pin Type Flanged Coupling 323
18.5.5 Oldham Coupling 324
18.5.6 Universal Coupling 326
18.5.7 Plummer Block 327
18.5.8 Swivel Bearing 329
18.5.9 Foot-step Bearing 329
18.5.10 C-clamp 331
18.5.11 Crane Hook 332
18.5.12 V-Belt Drive 334
18.5.13 Screw Jack 335
18.5.14 Pipe Vice 335
18.5.15 Speed Reducer 335

Part Drawings
19.1 Introduction 355
19.2 Engine Parts 356
19.2.1 Petrol Engine Connecting Rod 356
19.2.2 Marine Engine Connecting Rod End 357
19.2.3 Steam Engine Connecting Rod End 357
19.2.4 Spark Plug 357
19.2.5 Steam Engine Crosshead 357
19.2.6 Automobile Gear Box 362
19.2.7 Split-sheave Eccentric 366
19.3 Machine Tool Parts and Accessories 366
19.3.1 Tool Post 366
19.3.2 Lathe Slide Rest 366
19.3.3 Lathe Speed Gear Box 368
19.3.4 Milling Machine Tail Stock 370
19.3.5 Lathe Travelling Rest 370
19.3.6 Self-centering Vice 370
19.3.7 Milling Fixture 376
19.3.8 Indexing Drill Jig 376
19.3.9 Pierce and Blank Tool 376
19.4 Miscellaneous Parts 376
19.4.1 Blow-off Cock 376
19.4.2 Steam Stop Valve 381
19.4.3 Ramsbottom Safety Valve 381
19.4.4 Diaphragm Regulator 381
19.4.5 Angle Plummer Block 381
19.4.6 Castor Wheel 388
19.4.7 Speed Reducer 388

Peoduction Drawings
20.1 Introduction 389
20.2 Types of Production Drawings 389
20.2.1 Detail or Part Drawings 389
20.2.2 Working Assembly Drawings 392
20.2.3 Detailed Drawings and Manufacturing Methods 392
20.3 Example 393
20.3.1 Petrol Engine Connecting Rod 393

Computer Aided Drafting
21.1 Introduction 397
21.2 Overview 397
21.3 Required Equipment 397
21.3.1 Computer 397
21.3.2 Terminal 398
21.3.3 Keyboard 398
21.3.4 Cathode Ray Tube (CRT) 398
21.3.5 Plotters 398
21.3.6 Printers 398
21.3.7 Digitizers 398
21.3.8 Locators and Selectors 398
21.4 Display Technology 398
21.4.1 Plotting the Drawings 399
21.5 Basics of Operating System 399
21.6 Starting AutoCAD 399
21.6.1 Invoking AutoCAD Commands 400
21.6.2 Interactive Techniques 400
21.7 Planning for a Drawing 402
21.7.1 Co-ordinate System 402
21.7.2 Basic Geometric Commands 403
21.7.3 Drawing Entity-POINT 403
21.7.4 Drawing Entity-LINE 404
21.7.5 Drawing Entity-ELLIPSE 405
21.7.6 Drawing Entity-POLYGON 405
21.7.7 Drawing Entity-RECTANGLE 406
21.7.8 Drawing Entity-CIRCLE 406
21.7.9 Drawing Entity–ARC 407
21.8 Object Selection 407
21.8.1 Edit Commands 408
21.8.2 Zoom Command 409
21.8.3 Cross-hatching and Pattern Filling 410
21.8.4 Utility Commands 410
21.9 Types of Modelling 411
21.9.1 2D Wire Frame 411
21.9.2 3D Wire Frame 411
21.9.3 Surface Modelling 411
21.9.4 Solid Modelling 411
21.10 View Point 412
21.10.1 V-point Co-ordinates View(s) Displayed 413
21.11 View Ports 413
21.12 Creation of 3D Primitives 414
21.12.1 To Draw a Cylinder 414

21.12.2 To Draw Cone 415
21.12.3 To Draw a Box 415
21.13 Creation of Composite Solids 415
21.13.1 To Create Regions 415
21.13.2 Solid Modelling 416
21.13.3 Mass Property 416
21.14 Sectional View 416
21.15 Isometric Drawing 417
21.15.1 Setting Isometric Grid and Snap 417
21.16 Basic Dimensioning 417
21.16.1 Dimensioning Fundamentals 418
21.16.2 Dimensioning Methods 418
21.16.3 Linear Dimensions 419
21.16.4 Continuing Linear Dimensions 419
21.16.5 Example for Dimensioning 420
21.17 Polyline (Pline) 421
21.18 Offset 422
21.19 Elevation and Thickness 423
21.20 Change Prop 424
21.21 Extrusion 424