READOS / Manufacturing / KEVOS® original book
Welding Distortion by the Numbers
Why welds pull parts out of shape, how much they shrink, bow, twist and buckle, and how sequence, presetting, restraint and straightening control it
Understand and control welding distortion with numbers: shrinkage, gap closure, bowing, angular distortion, buckling, restraint, welding sequence, presetting and straightening.
Start readingAbout this book
Every weld shrinks as it cools, and the shrinkage pulls on the parts it joins. A butt-welded plate draws its edges together and kinks at the seam; a beam with a stiffener welded on one side bows; a flange tilts away from a fillet weld; a thin panel buckles into a wavy surface. Distortion costs fabricators time in straightening, machining and rework, and sometimes scraps parts outright. Most of it can be predicted, at least roughly, and much of it can be prevented by choices made before the first arc is struck.
This book is for fabricators, welding supervisors, designers and manufacturing engineers. It assumes basic physics and strength of materials in SI units. It explains, with numbers, why welds shrink, how much shrinkage to expect across and along a weld, how it turns into bowing, angular distortion and buckling, how restraint trades distortion for stress and cracking, and how welding sequence, presetting, fixtures and straightening control it.
Early manuals as a starting point
The early welders understood distortion from hard experience. The Davis-Bournonville course of 1919 told its students that whatever is expanded by heat must contract again, and that a welder who tried to prevent expansion or contraction was likely to crack the joint or something else. Campbell’s Army manual of the same year showed how to jack a cast pulley wheel apart before welding a broken spoke, so that the weld’s contraction would bring it back to shape. And Herbert L. Whittemore, testing welds at the University of Illinois in 1910, clamped the test plates with their edges open at the far end to allow for what Whittemore called creep, the drawing together of the edges ahead of the weld as the metal behind it cooled; when the allowance was left out, the plates warped badly.
Those observations are the foundations of distortion control. Each chapter takes one of them, puts numbers on it, and applies it to a modern fabrication.
The running case
This is an illustration. A fabrication shop builds welded steel products: plate girders for small bridges and platforms, base frames for machines, and thin stainless steel panels for food-processing equipment. It has had trouble with girders that bow, frames whose mounting faces do not sit flat, and panels that buckle, and its production manager wants to understand the causes and control them.
The shop, its products, measurements and costs are invented for teaching. They are not KEVOS® work. Real structures and products are made to the applicable standards and specifications, which set tolerances on straightness, flatness and dimensions.
How to use the book
Chapter 1 explains why welds distort. Chapters 2 and 3 cover shrinkage across and along a weld, Chapter 4 angular distortion and Chapter 5 buckling of thin plate. Chapter 6 deals with restraint and residual stress. Chapters 7 and 8 cover welding sequence and presetting with fixtures, Chapter 9 straightening, and Chapter 10 planning distortion control and keeping the record. Every chapter ends with an exercise and its worked answer.
Limits and professional responsibility
This book is educational. The shrinkage estimates in it are illustrations based on simplified models; real distortion depends on many factors and is best confirmed by measurement on the shop’s own work. Straightening by heat can damage some steels and must follow the material’s limits. Structures and products must meet the tolerances of their applicable standards and specifications.
An original treatment
READOS covers shrinkage and welding sequence in plate repairs in Weld Repairs That Hold, and straightening of shafts in Machine Part Repairs by the Numbers; this book covers distortion in new fabrication and links to them. The explanations, the fabrication case, the calculations, figures and exercises are original KEVOS® writing. The historical sources are public-domain works in the United States; their observations are summarised in new words, and none of their text, tables or figures is reproduced.
Who this book is for
Fabricators, welding supervisors, designers and manufacturing engineers who need welded parts to come out the right size and shape, and want to predict and control distortion rather than fight it afterwards.
What you will learn
- Explain how heating, yielding and cooling make welds shrink and pull parts out of shape.
- Estimate transverse shrinkage, gap closure, longitudinal bowing and angular distortion.
- Recognise when thin plate will buckle and when restraint will crack a joint instead.
- Plan welding sequences, presetting and fixtures that cancel distortion.
- Straighten distorted work safely and record what controls worked.
Inside this book
Chapters
- 01Why welds distortFollow a weld from heating to cooling: expansion held back by cold metal, yielding at a temperature rise of about a hundred degrees, and the shrinkage left behind that pulls parts out of shape.
- 02Transverse shrinkage and closing gapsEstimate how much a butt weld draws its plates together, see how groove shape changes it, allow for it in cutting, and control the closing of the gap ahead of the arc that Whittemore called creep.
- 03Longitudinal shrinkage and bowingTreat a weld's shrinkage along its length as a tensile force, calculate the bow it causes off the neutral axis, and see why sequence and symmetry decide whether long members come out straight.
- 04Angular distortionSee why a weld wider at its face than its root kinks the plates it joins, measure flange tilt at fillet welded tees, and reduce it with double-sided grooves, balanced sequences and smaller welds.
- 05Buckling of thin plateCalculate the stress at which a thin panel buckles, see why welding's residual compression easily exceeds it, and keep thin stainless and steel panels flat with heat control, spacing and fixtures.
- 06Restraint and residual stressSee how holding a joint still turns its shrinkage into residual stress near yield, why restrained joints crack, how locked-in stress moves parts when machined, and how stress relief helps.
- 07Welding sequence and balanceUse the order of welding to cancel distortion: balance about the neutral axis, back-step and skip welding along seams, middle-out sequences, sub-assemblies and a written sequence for critical work.
- 08Presetting, pre-bending and fixturesSet parts at the opposite angle so welding pulls them true, pre-bend girders against their expected bow, calibrate presets by measurement, and design fixtures that control distortion without cracking.
- 09Straightening distorted workStraighten welded members with heat triangles, line heats and spot heats, estimate the correction each heat gives, respect the steel's temperature limits, and know when a press or jack is better.
- 10Planning distortion control and keeping the recordBuild a distortion control plan for each product, from its tolerance through prediction to the cheapest controls that work, measure the results, and keep the record that lets the shop improve.
References and source notes
The manuscript and worked examples are original KEVOS® writing. References inform particular concepts; their authors do not endorse this book. Web references were consulted on 25 October 2026.
- Herbert L. Whittemore. The strength of oxyacetylene welds in steel (University of Illinois Engineering Experiment Station, Bulletin No. 45) (1910). Historical source for the allowance made for plate edges drawing together during welding, which the report called creep, and the warping of a joint welded without it, cited in Chapter 2. Summarised in new words; no text, tables or figures are reproduced.
- Davis-Bournonville Company, Jersey City. Davis-Bournonville Oxy-Acetylene Welding and Cutting Course of Instruction (1919). Historical source for its lecture on expansion, contraction and preheating, including the cracking of castings welded without preheat and the need to allow metal to expand and contract freely. Summarised in new words.
- Lorn Campbell Jr. (John Wiley & Sons, New York). Oxy-Acetylene Welding Manual (1919). Historical source for allowing for contraction in welding confined parts such as pulley wheel spokes, and the welder's need to study expansion and contraction. Summarised in new words.
- M. Keith Dunham (Norman W. Henley Publishing, New York). Automobile Welding with the Oxy-Acetylene Flame (1917). Historical source for the limits of clamping and V-blocks in holding alignment during welding, and for welding thin sheet from the middle outwards. Summarised in new words.
