The repair of vehicle bodies

The Repair of Vehicle Bodies

This well-respected book has been revised and updated, with an additional chapter on setting up a new

bodyshop as well as many updated sections and a range of revision questions. It also contains skill building

notes covering all aspects of construction, repair and finishing for Vehicle Body Repair students. Serving as a

comprehensive manual, this book fully covers the underpinning knowledge required for the Automotive

Skills Council Vehicle Body and Paint Operations requirements, IMI Body Repair and Refinishing Technical

Certificates (VRQs), National Vocational Qualifications (NVQs), City & Guilds Vehicle Body Repair

Competence courses, and the NVQ and Progression Awards of both City & Guilds and the Institute of the

Motor Industry at levels 2 and 3.

The most comprehensive text on the construction, repair and finishing of vehicle bodies.

Updated and revised to meet the latest Automotive Skills standards, IMI Technical Certificate curriculum

and NVQ requirements.

Ideal for body repair work, refinishing, painting and hobby vehicle builders.

Automotive HND and degree students will find the text valuable for practical project work.

This text is essential reading for all of those involved in body repair work or insurance assessment, as well as

for professional vehicle restorers and DIY enthusiasts working on the restoration or adaption of classic and

modern cars.

Andrew Livesey has been involved in automotive engineering both as a lecturer and a writer for many years.

He taught and managed the Oxford Brookes University Motorsport programmes at Brooklands and set up

the very successful undergraduate training programmes for McLaren. He is the author of several motor

vehicle books and currently divides his time between lecturing at the University of Kent and running his own

company, Andrew Livesey Consulting Ltd.

Other books by Andrew Livesey:

Basic Motorsport Engineering, ISBN: 978-0-750-68909-0

Advanced Motorsport Engineering, ISBN: 978-0-750-68908-3

The Repair of Vehicle Bodies

Sixth edition

The late A. ROBINSON

RTechEng, MInstBE, MIBCAM, AWeldl, MISME

Formerly Section Leader for Vehicle Bodywork and Vehicle Body Repair

Course Coordinator for CGLI 398 Vehicle Body Competencies

Course Coordinator for CGLI 385 Vehicle Bodywork at Gateshead College

Updated by

Eur Ing ANDREW LIVESEY MA CEng MIMechE FIMI

Sixth edition published 2013

by Routledge

2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN

Simultaneously published in the USA and Canada

by Routledge

711 Third Avenue, New York, NY 10017

Routledge is an imprint of the Taylor & Francis Group, an informa business

© 2013 Andrew Livesey and A. Robinson

The right of Andrew Livesey and A. Robinson to be identified as authors of

this work has been asserted by them in accordance with sections 77 and 78 of the Copyright,

Designs and Patents Act 1988.

All rights reserved. No part of this book may be reprinted or reproduced or utilized

in any form or by any electronic, mechanical, or other means, now known or

hereafter invented, including photocopying and recording, or in any information storage or

retrieval system, without permission in writing from the publishers.

Trademark notice: Product or corporate names may be trademarks or registered

trademarks, and are used only for identification and explanation without intent to

infringe.

First edition published by Heinemann Educational Books Ltd 1973

Fifth edition published by Butterworth-Heinemann 2005

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication Data

Robinson, A. (Alan)

Repair of vehicle bodies / A. Robinson ; updated by Andrew Livesey. -- 6th ed.

p. cm.

Includes index.

1. Automobiles--Bodies--Maintenance and repair. 2. Automobiles--Design and construction.

I. Livesey, W. A. (W. Andrew) II. Title.

TL255.R56 2013

629.20

60288--dc23

2012025441

ISBN: 978-0-415-53445-1 (pbk)

ISBN: 978-0-203-07547-0 (ebk)

Typeset in Times

by Integra Software Services Pvt. Ltd, Pondicherry, India

NOTICE

No responsibility is assumed by the publisher for any injury and/or damage to persons or

property as a matter of products liability, negligence or otherwise, or from any use or operation of

any methods, products, instructions or ideas contained in the material herein. Because of rapid

advances in the medical sciences, in particular, independent verification of diagnoses and drug

dosages should be made.

To my wife Jean for her help and support whilst writing

and my dog Lettie for taking me on walks along

the beach to think through concepts

Contents

List of figures xii

List of tables xxii

Preface xxiii

Acknowledgements xxiv

1 Vehicle construction 1

Vehicle safety testing 1

Elements of vehicle construction 2

Vehicle information code plate 6

Skills and questions 6

2 Health and safety, and the environment 8

Personal health and safety procedures 8

Fire precautions 10

Fire risks in the workshop 11

Safety signs in the workshop 14

General safety precautions in the workshop 14

Electrical hazards 16

Control of Substances Hazardous to Health (COSHH) Regulations 16

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 16

Maintain the health, safety and security of the work environment 16

Minimizing the risks from unavoidable hazards 18

Skills and questions 23

3 Hand and power tools 24

Hand tools used in body repair work 24

Hammers 24

Hand dollies 26

Body spoons 27

Body files 28

Hand snips 28

Specialist panel beating tools 29

Clamps 30

Punches 30

Edge setters or jogglers 30

Sheet metal bench stakes 31

Hand grooving tools 33

Rivet sets 33

Cutting tools 33

Bending and swaging tools 34

General-purpose assembly and dismantling tools 35

Skills 41

Questions 41

4 Materials used in vehicle bodies 43

Skills 43

Steel 43

Aluminium 51

Rubber 54

Sealers 54

Sound deadening, thermal insulating and undersealing materials 56

Interior furnishings 57

Plastics 58

Amorphous and crystalline plastics 58

Abbreviations for automotive plastics 60

Types of plastics 61

Repair procedures 63

Painting plastics 64

Safety glass 64

Skills 66

Questions 67

5 Metal forming processes 68

Properties of metals 68

Heat treatment of steel and aluminium 71

Heat treatment of carbon steel 72

Machines for sheet metal fabrication 76

Cutting machines 77

Bending theory 79

Bending machines 79

Rolling machines 80

Forming and drawing 85

Sheet metal cutting for press work 86

Skills 88

Questions 88

6 Marking out and measuring 89

Marking out 89

Manufacture of templates 89

Basic marking-out and measuring instruments 90

Precision marking-out and measuring instruments 97

Skills 101

Questions 101

7 Methods of joining 102

Solid rivets 102

Types of riveted joint 103

Blind rivets 105

Repetition rivets 109

Rivet selection 111

Structural fasteners 112

Screws and bolts 115

Fastening devices 121

Adhesives 126

Selection of adhesives 127

Achieving good results with adhesives 127

viii Contents

Adhesives and the automotive industry 128

Skills 130

Questions 131

8 Soft and hard soldering methods 132

Comparison of fusion and non-fusion jointing processes 132

Soft and hard solders 133

Soft soldering 133

Hard soldering 137

Health and safety and the environment 144

Skills 144

Questions 144

9 Gas welding, cutting and plasma arc 146

Development of gas welding 146

Systems of gas welding 147

Oxy-acetylene welding equipment 148

Regulators 150

De

finitions of welding terms 153

Welding rods and

fluxes 154

Flame control and types of

flame 154

Methods of welding 156

Edge preparation and types of joint 157

Welding technique: butt joint in mild steel 159

Welding various metals 160

Gas cutting 160

Gases: characteristics and colour coding 163

Safety measures 163

Plasma arc cutting 167

Skills 170

Questions 170

10 Electric resistance welding 172

Resistance welding in car body manufacture 172

Resistance spot welding 173

Resistance projection welding 174

Resistance seam welding 175

Resistance

flash welding 176

Resistance butt welding 176

Resistance welding in body repair work 176

Resistance spot welding of high-strength steels 177

Weld quality 177

ARO Spotrite Pulsa resistance welding system 181

Single-sided spot welding 184

Skills 185

Questions 185

11 Manual metal arc welding 187

Principles of manual metal arc welding 187

Electrical terms used in arc welding 188

Metal arc welding equipment 188

Electrodes used in welding: BS coding 191

Arc welding positions 193

Essential factors of arc welding 194

Technique of welding 198

Contents ix

Safety precautions for the welder 199

Skills 200

Questions 200

12 Gas shielded arc welding 201

Development of gas shielded arc welding 201

Gases used for shielded arc processes 201

TIG welding 204

Equipment used in TIG welding 205

Application of TIG welding 210

MIG/MAG welding 210

MIG/MAG spot/plug welding 211

Equipment used in MIG/MAG welding 212

MIG/MAG welding techniques 217

Applications of MIG/MAG welding in vehicle body construction 221

Applications of MIG/MAG welding in body repair work 222

MIG/MAG welding of low-carbon steel and HSLA steels 224

Welding stress and distortion in the MIG/MAG process 225

Weld testing and inspection 228

Equipment maintenance and safety 230

Skills 231

Questions 231

13 Craft techniques and minor accident damage 232

Panel beating: forming panels by hand 232

Shaping metal by hand 232

General guide to the fabrication of hand-made panels 239

Edge stiffening of sheet metal 240

Techniques of damage recti

fication 243

Hammering techniques 245

Filing 249

Sanding or disc grinding 250

Hot shrinking 250

Cold shrinking 252

Body soldering 253

Chemically hardening

fillers (plastic

fillers) 254

Body jack (hydraulic) 256

Application of the body jack 259

Repair of component motor body panels 262

Aluminium panel repair 267

Body electrical and electronic systems 273

Skills 278

Questions 278

14 Major accident damage repair 280

Damage classi

fication and assessment 280

Pulling, alignment and repair systems used on major accident damage 281

Alignment of the modern integral body 285

Major repair techniques 293

Questions 316

15 Bodyshop planning 318

Initial planning 318

Planning the areas of the workshop 321

Bodyshop heating 326

x Contents

Bodyshop lighting 328

Essential equipment for the bodyshop 329

Bodyshops and legal requirements 331

Questions 340

16 Reinforced composite materials 341

Introduction 341

Basic principles of reinforced composite materials 341

Manufacture of reinforced composite materials 342

Types of reinforcing material 343

Resins used in reinforced composite materials 346

Moulding techniques for reinforced composite laminates 350

Repair of reinforced composite bodies 357

Common faults in moulded laminates 359

Safety precautions 362

Skills 363

Questions 363

17 Automotive finishing and refinishing 365

Glossary of terms used in spray painting 365

Basic composition of paint 366

Types of paint 366

Materials used in refinishing 368

Spray painting equipment 371

Types of spray gun 373

Basic parts of a standard spray gun 375

Spray gun maintenance and cleaning 377

Spray gun motion study 379

Spraying defects 382

Sanding and polishing machines 384

Preparation of a motor vehicle for repainting 386

Finishing and refinishing processes 387

Burnishing, polishing and final detail work 398

Rust-proofing 399

Movement of vehicle in the paint shop 400

Common spray painting defects 401

Colour mixing and matching 403

Questions 404

18 Case study 406

General appearance 406

Site selection 406

Pre-planning 406

Notable points 408

Glossary 411

Websites 419

Index 420

Contents xi

Figures

1.1a Frontal impact test 2

1.1b Side impact test 2

1.1c Pole test 2

1.1d Pedestrian impact tests 2

1.2 Front end construction (a) integral or mono, (b) composite and (c) front and rear sub-frames;

these are bolted separately to the body assembly 3

1.3 Main floor assemblies and boot floor assemblies (Proton) 4

1.4 Body side assemblies, roof, BC-post, front and rear door of a hatchback (Proton) 5

1.5 Location of vehicle information code plate 6

1.6 Code plate descriptions 6

2.1 The fire triangle 11

2.2 Types of portable fire extinguishers 13

2.3 Choice of fire extinguishers 13

2.4 Standard safety signs 14

3.1 From left to right: (a) standard bumping hammer with flat faces; (b) bumping hammer with

crown faces; (c) pick and finishing hammer 25

3.2 From left to right: (a) utility dolly; (b) curved dolly; (c) double-ended dolly; (d) shrinking dolly 26

3.3 Spoon dolly 27

3.4 Flexible panel file 28

3.5 Universal combination snips – left handed 28

3.6 Zipcut spot-weld remover (Sykes-Pickavant Ltd) 29

3.7 Door skinner tool 30

3.8 (a) Engineer’s ball-pein hammer; (b) stretching and flanging hammer; (c) wiring hammer;

(d) hollowing or blocking hammer 31

3.9 Sheet metal bench stakes 32

3.10 What can be regarded as a full set of tools (Facom Tools Ltd) 37

3.11 Air chisel set 38

3.12 Cordless drill-driver 39

3.13 Corded orbital sander 40

4.1 Body shell panels showing galvanized protection (Motor Insurance Repair Research Centre) 47

4.2 Types of sealed joints used in vehicle bodywork 55

4.3 Plastic ID markings 62

5.1 Changes in structure of carbon steel with temperature and carbon content 73

5.2 Strength in crowned surfaces 76

5.3 Strength in angles and flanges 76

5.4 Strength in U-channel and box sections 76

5.5 The cutting section showing a sheared piece of metal 77

5.6 Blade clearance 77

5.7 Bending action 79

5.8 Bending allowance 79

5.9 Pinch rolls 81

5.10 Pyramid rolls 81

5.11 Swaging attachments 83

5.12 Brake press dies and applications 84

5.13 Box drawing 86

5.14 Metal flow during drawing 87

5.15 Metal punching 87

6.1 Marking out with a scriber and rule (Neill Tools Ltd (Eclipse)) 90

6.2 Engineer’s scriber (double-ended) (Neill Tools Ltd (Eclipse)) 91

6.3 Straight edges (with square or bevelled edges) (Neill Tools Ltd (Eclipse)) 91

6.4 (a) Centre punches, (b) nail punches, (c) parallel pin punch (Neill Tools Ltd (Eclipse)) 92

6.5 Try square (Neill Tools Ltd (Moore and Wright)) 92

6.6 Combination square (Neill Tools Ltd (Moore and Wright)) 93

6.7 Spring dividers (Neill Tools Ltd (Moore and Wright)) 94

6.8 Trammel heads (Neill Tools Ltd (Eclipse)) 94

6.9 Calipers (Neill Tools Ltd (Moore andWright)) 95

6.10 Oddleg calipers (Neill Tools Ltd (Moore and Wright)) 95

6.11 (a) Reversible depth gauge, (b) protractor depth gauge (Neill Tools Ltd (Moore and Wright)) 96

6.12 Feeler gauge (Neill Tools Ltd (Moore and Wright)) 96

6.13 Screw pitch gauge (Neill Tools Ltd (Moore and Wright)) 96

6.14 Radius gauges (external and internal radii) (Neill Tools Ltd (Moore and Wright)) 97

6.15 Drill gauge (Neill Tools Ltd (Moore and Wright)) 97

6.16 Wire gauges (metric) (Neill Tools Ltd (Moore and Wright)) 98

6.17 Universal surface gauges (Neill Tools Ltd (Eclipse)) 98

6.18 Vee blocks 99

6.19 Engineer’s levels (Neill Tools Ltd (Moore and Wright)) 99

6.20 Vernier caliper gauge (Neill Tools Ltd (Moore and Wright)) 100

6.21 Micrometer (Neill Tools Ltd (Moore and Wright)) 100

6.22 External micrometers (Neill Tools Ltd (Moore and Wright)) 100

7.1 Small rivet heads (BS 641) 103

7.2 Single-riveted lap joint 103

7.3 Double-riveted butt joint 104

7.4 Riveting procedure 104

7.5 POP blind rivet, standard open type: setting sequence (Tucker Fasteners Ltd) 105

7.6 POP blind rivet: standard open type (Tucker Fasteners Ltd) 106

7.7 Types of POP blind rivet (Tucker Fasteners Ltd) 107

7.8 POP blind rivet: sealed type (Tucker Fasteners Ltd) 107

7.9 POP blind rivet, sealed type: setting sequence (Tucker Fasteners Ltd) 107

7.10 POP blind rivet: grooved type (Tucker Fasteners Ltd) 108

7.11 POP blind rivet, grooved type: setting sequence (Tucker Fasteners Ltd) 108

7.12 POP blind rivet, peel type: before setting (Tucker Fasteners Ltd) 108

7.13 POP blind rivet, peel type: after setting (Tucker Fasteners Ltd) 109

7.14 Special POP rivets (Tucker Fasteners Ltd) 109

7.15 Blind rivet nut, installation sequence 109

7.16 The Chobert hollow rivet (Avdel Ltd) 110

7.17 The Chobert grooved rivet (Avdel Ltd) 110

7.18 The Chobert and Grovit riveting systems (Avdel Ltd) 110

7.19 Briv placing sequence (Avdel Ltd) 110

7.20 Hand operated riveting tool, plier type (Tucker Fasteners Ltd) 111

7.21 Hand operated riveting tool, lever type (Tucker Fasteners Ltd) 111

List of figures xiii

7.22 Hand operated riveting tool, lazy tongs type (Tucker Fasteners Ltd) 111

7.23 Automatic riveting system (Tucker Fasteners Ltd) 112

7.24 The Avdelok fastener (Avdel Ltd) 112

7.25 The Avdelok system (Avdel Ltd) 112

7.26 Hemlok fastener (Avdel Ltd) 113

7.27 Hemlok placing sequence (Avdel Ltd) 113

7.28 Standard Nutsert (Avdel Ltd) 114

7.29 (a) Standard Nutsert placement, (b) thin sheet Nutsert with bolt in place (Avdel Ltd) 114

7.30 Monobolt and placing sequence (Avdel Ltd) 114

7.31 Avtainer and placing sequence (Avdel Ltd) 115

7.32 Unhardened wood screws (European Industrial Services Ltd) 116

7.33 Fixing self-tapping screws (European Industrial Services Ltd) 116

7.34 Supadriv Taptite thread forming screw (European Industrial Services Ltd) 116

7.35 AB type self-tapping screw (European Industrial Services Ltd) 116

7.36 CA Taptite screw (European Industrial Services Ltd) 116

7.37 Plastite screw (European Industrial Services Ltd) 117

7.38 Polymate screw (European Industrial Services Ltd) 117

7.39 Hammer driven screw (European Industrial Services Ltd) 117

7.40 Screw nail (European Industrial Services Ltd) 117

7.41 (a) Bolt, (b) set-screw, (c) coach bolt 118

7.42 Bolt identification 118

7.43 Machine screw head types: slotted and (a) countersunk, (b) round, (c) cheese,

(d) mushroom, (e) pan; Pozidriv and (f) countersunk, (g) pan; socket and (h) cap,

(i) countersunk, (j) cup point (European Industrial Services Ltd) 119

7.44 Nut identification 119

7.45 Clinch nut (European Industrial Services Ltd) 120

7.46 Clinch nut fixing procedure (European Industrial Services Ltd) 120

7.47 (a) Nyloc, (b) Cleveloc nuts (Forest Fasteners) 120

7.48 Spire speed nut (Forest Fasteners) 121

7.49 U type captive nut (Forest Fasteners) 121

7.50 J type captive nut (Forest Fasteners) 122

7.51 Nut grip (Forest Fasteners) 122

7.52 Cable clip used for latching: sectional view shows clip in position in a panel (Forest

Fasteners) 122

7.53 (a) Simple push-on clip showing clip in position, (b) tubular clip, showing fitting sequence

(Forest Fasteners) 123

7.54 Plastic capture nut (TRW United-Carr Ltd) 123

7.55 Plastic push-in panel fasteners: (a) W-button, (b) Christmas-tree button (TRW United-Carr Ltd) 124

7.56 Trim panel fasteners (TRW United-Carr Ltd) 125

7.57 Quick-release fasteners, quarter turn (TRW United-Carr Ltd) 125

7.58 Edge fasteners, D type (TRW United-Carr Ltd) 125

7.59 Simplified cross-sectional representation of a typical joint (Permabond Adhesives Ltd) 128

7.60 Adhesive joint design (Permabond Adhesives Ltd) 129

7.61 Toughened adhesive: when overloaded, crack propagation is stopped by the dispersed

rubbery phase (Permabond Adhesives Ltd) 130

8.1 Capillary attraction through a soldered lapped joint 133

8.2 Soldering bits 136

8.3 Soldering process 136

8.4 Types of soft soldered joints 137

8.5 Joint design for brazing, showing the brazing equivalents to welding 140

xiv List of figures

9.1 Low-pressure welding equipment 147

9.2 High-pressure gas welding equipment in use (Murex Welding Products Limited) 147

9.3 A typical oxy-fuel gas welding and cutting system 148

9.4 Cylinder valve (BOC Ltd) 148

9.5 Typical cylinder label (BOC Ltd) 149

9.6 Identification markings on gas cylinder necks (BOC Ltd) 150

9.7 Welding and cutting blowpipe, high pressure (Murex Welding Products Limited) 150

9.8 Oxygen regulator (Murex Welding Products Ltd) 151

9.9 Acetylene regulator (Murex Welding Products Ltd) 151

9.10 Flashback arresters for oxygen and acetylene regulators (Murex Welding Products

Limited) 152

9.11 Hose fittings: nut, nipple and O-clips (Murex Welding Products Ltd) 152

9.12 Hose check valves (Murex Welding Products Ltd) 152

9.13 Types of welding goggles (Murex Welding Products Limited) 153

9.14 Section through a welded joint 154

9.15 Flame temperature 154

9.16 Regulation of welding flame 155

9.17 Methods of welding: (a) the leftward method and (b) the rightward method 156

9.18 Edge preparation 158

9.19 Flame cutting process (BOC Ltd) 160

9.20 Cutting torches (Murex Welding Products Limited) 161

9.21 Types of cutting torches (BOC Ltd) 161

9.22 (a) Injector cutting torch and two-seat nozzle, (b) three-seat nozzle (BOC Ltd) 162

9.23 (a) One-piece acetylene nozzle, (b) two-piece LPG nozzle (BOC Ltd) 162

9.24 Cutting technique (BOC Ltd) 162

9.25 Acetylene cylinders in fires (BOC Ltd) 166

9.26 Simplified diagram of plasma arc cutter (Motor Insurance Repair Research Centre) 167

9.27 Plasma cutting unit: three phase, 40 amperes (Olympus Welding Supplies Ltd) 168

9.28 An air-cooled plasma cutting torch (SIP (Industrial Products) Ltd) 168

9.29 Plasma arc cutting torch nozzle, showing position of electrode (Motor Insurance Repair

Research Centre) 169

10.1 Stationary pedestal spot welding machine (SIP (Industrial Products) Ltd) 173

10.2 Portable spot welding machine in use (SIP (Industrial Products) Ltd) 174

10.3 (a) Resistance spot welding system, (b) relationship between weld formation, current and

pressure in welding 174

10.4 Projection welding system seam welding 175

10.5 Continuous resistance 175

10.6 Seam welding (stitch welding) 175

10.7 Flash welding 176

10.8 Resistance butt welding 176

10.9 Body panels made from high-strength/galvanized steels (Motor Insurance Repair Research

Centre) 178

10.10 Welding together panels of the same thickness (Motor Insurance Repair Research Centre) 179

10.11 Types of electrode profile (Motor Insurance Repair Research Centre) 179

10.12 Current shunting in resistance welds positioned in close proximity 180

10.13 (a) Peel test, (b) destructive test (Motor Insurance Repair Research Centre) 181

10.14 Modes of spot weld failure (Motor Insurance Repair Research Centre) 181

10.15 CEBORA spot welder (Mig Tig Arc) 182

10.16 Electrode arm sets for different makes of vehicles (SIP (Industrial Products) Ltd) 183

10.17 Single-sided and double-sided spot welding equipment (Stanners Ltd) 184

List of figures xv

11.1 (a) Principles of metallic arc welding, (b) cross-section of a coated electrode in the

process of welding 188

11.2 Diesel engined DC generator and circuit 189

11.3 AC transformers and circuit (Murex Welding Processes Ltd) 189

11.4 Arc welding positions 193

11.5 Correct arc length 194

11.6 Tapping method of striking the arc 195

11.7 Correct speed and current setting 195

11.8 Scratching method of striking the arc 195

11.9 Undercutting 196

11.10 Overlapping 196

11.11 Types of arc welded joint 196

11.12 Basic joint types: (a) fillet, (b) butt, (c) lap (BOC Ltd) 197

11.13 Static loading conditions: (a) butt weld, (b) fillet weld, load carrying area

shaded (BOC Ltd) 197

11.14 Acceptable and undesirable joint detail (BOC Ltd) 197

11.15 Plate preparation for limited access butt joints: (a) permanent backing strip,

(b) fusible insert, (c) U preparation for root access (BOC Ltd) 198

12.1 TIG welding equipment AC/DC (Murex Welding Products Ltd) 202

12.2 MIG welding equipment (Migatronic Welding Equipment Ltd) 202

12.3 Basic principles of the TIG welding process (BOC Ltd) 205

12.4 Principles of the TIG welding process 206

12.5 Recommended edge preparation 207

12.6 Principles of the TIG spot-welding process 207

12.7 Gas, water and power supply for TIG welding 208

12.8 Alternative methods of DC connections: (a) theoretical distribution of heat in the argon

shielded arc with the alternative methods, (b) average differences in arc voltages with equal

arc lengths, using (left) negative polarity at the electrode and (right) positive, (c) relative

depths of penetration obtainable with (left to right) DC positive, DC negative and AC 209

12.9 A water-cooled TIG welding torch 209

12.10 Appropriate vertex angles of electrodes (BOC Ltd) 209

12.11 Recommended angles for torch and filler rod in TIG welding 209

12.12 Motion of torch and filler rod for TIG welding heavy sections 210

12.13 Basic principles of operation of MIG/MAG welding (BOC Ltd) 211

12.14 Principles of the MIG/MAG welding process: argon, argon/CO2 or CO2 211

12.15 MIG welding control panel (Migatronic Welding Equipment Ltd) 213

12.16 Metal transfer forms 215

12.17 Air-cooled MIG welding torch (Murex Welding Processes Ltd) 216

12.18 Migatronic Dialog torch with current control in the torch handle (Migatronic

Welding Equipment Ltd) 217

12.19 Wire feed unit (Migatronic Welding Equipment Ltd) 217

12.20 Incorrect settings for wire speed (Stanners Ltd) 218

12.21 Weld defects and their causes 219

12.22 Welding position (Migatronic Welding Equipment Ltd) 220

12.23 Typical MIG/MAG welding positions 220

12.24 Tack weld 220

12.25 Continuous weld 220

12.26 Making a plug weld 221

12.27 MIG/MAG spot welding 221

12.28 Lap spot weld 221

xvi List of figures