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Deep Drawing and Spinning by the Numbers

Cups, shells and covers from flat sheet: blank sizes, draw ratios, forces, tooling, earing, ironing, annealing, spinning and the choice between them

Work out drawn and spun sheet metal parts with numbers: blank size, draw ratios and redraws, press force, blank holding, die clearance, trim, ironing, spinning and draw-or-spin costs.

10 chapters · About 100 minutes · Free to read · Intermediate sheet metal forming and tooling

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KEVOS® LibraryMANUFACTURINGØ24Deep Drawing andSpinning by theNumbersKEVOS® ORIGINAL BOOK10 CHAPTERS

About this book

A drawn or spun part begins as a flat blank and ends as a cup, a shell, a cover or a cone without a seam. The metal does not stretch much to get there. It flows: the blank’s outer ring is pulled inwards and gathered into a wall, its circumference shrinking as its radius falls. Whether that flow succeeds, or the part wrinkles, tears or splits, depends on a few numbers: the blank’s size, the ratio of the blank to the punch, the forces on the wall and the flange, the clearance and radii of the tools, and how hard the metal has become from the work already done on it.

This book works through drawing and spinning in the order a designer or manufacturing engineer meets them. It covers what the two processes do to the metal, blank sizes, draw ratios and redraws, drawing force and press capacity, blank holding and wrinkling, die clearance and radii, earing, trim and tolerances, ironing, work hardening and annealing, metal spinning and shear spinning, and the choice between drawing, spinning and other routes.

It suits product designers, manufacturing engineers, toolmakers, press shop supervisors and buyers. It assumes school algebra and a little geometry. Flat-pattern development of seamed sheet metal shapes is covered by Sheet Metal Patterns by the Numbers, and general sheet metal part design by Sheet Metal Parts by the Numbers; this book is about parts made from one blank without a seam.

The running case

Every chapter follows one fictional part. This is an illustration. SC-100 is a stainless steel sensor cover: a flat-bottomed cup with a mean diameter of 100 mm, a finished height of 70 mm and a bottom corner radius of 4 mm, drawn from 0.8 mm 304 stainless steel sheet. It protects an instrument on outdoor equipment, it must be seamless so that it seals against its base, and it is wanted in quantities that might be hundreds or tens of thousands a year. The material properties, limits and process figures used are illustrations chosen to show the method; a real part uses the supplier’s certified properties, the toolmaker’s experience and trials.

The part and its numbers are invented; none describes KEVOS® work or a real product. Prices, where they appear, are illustrations in Australian dollars excluding GST.

Who this book is for

Product designers, manufacturing engineers, toolmakers, press shop supervisors and buyers who design, make, quote or source drawn and spun cups, shells and covers in sheet metal.

What you will learn

  • Size a blank for a drawn cup from its surface area, with corner radii and a trim allowance.
  • Plan a part's draws and redraws from its draw ratios, and check each against the material's limit.
  • Estimate drawing and blank-holding forces, and choose a press with margin for both.
  • Set die clearance, radii, trim and ironing reductions, and plan annealing for work-hardening materials.
  • Size a spun or shear-spun part, and choose between drawing, spinning and other routes by quantity and cost.

Inside this book

Chapters

  1. 01What drawing and spinning do to the metalSee how a flat blank becomes a seamless cup: flange, wall and punch radius, constant volume and area, the family of drawing and spinning processes, and catch a wall thickness the process cannot give.
  2. 02Blank size from surface areaSize a drawn part's blank from its surface area: discs, corner radii, walls and flanges at mid-thickness, the trim allowance, blank layout in strip, and catch a blank sized like a bent part's.
  3. 03Draw ratios, reductions and redrawsMeasure how hard a draw is with its draw ratio, see what sets the limit, plan a part's first draw and redraws with margin, work out each stage's height, and catch a single draw planned at the limit.
  4. 04Drawing force and press capacityEstimate the punch force a draw needs from the wall's strength, add the blank holder's force, see where in the stroke a press can supply it, and catch a mechanical press rated at the wrong height.
  5. 05Blank holding, wrinkles and lubricationHold a drawing flange flat without tearing the wall: holder pressure and area through the stroke, profiled force, lubrication, and catch a tear cured by a holder force that wrinkled the cup.
  6. 06Die clearance, radii and tool sizesSize a drawing tool's punch and die from the part: clearance for a thickening wall, die and punch radii, finish, venting, and catch a clearance set to the sheet's thickness that ironed the rim.
  7. 07Earing, trim and tolerancesSee why a drawn rim comes out wavy, measure the sheet's anisotropy, build a trim allowance from ears, blank position and cut, choose a trimming method, and catch an allowance that left notches.
  8. 08Ironing, work hardening and annealingThin a drawn wall on purpose by ironing, follow how each stage hardens the metal, decide when an anneal is needed, and catch deeper stainless cups that split days after a redraw with no anneal.
  9. 09Metal spinning and shear spinningForm round parts on a lathe: conventional spinning's blanks, passes and cycle times, the sine law of shear spinning, and catch a cone's blank sized from the angle on the wrong side of its wall.
  10. 10Draw, spin or something elseChoose between drawing, spinning and other routes by quantity: tooling and unit costs, break-even, cost per part across volumes, uncertain demand, and catch tooling costed over a contract not yet won.

Related Tools and Examples

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 26 October 2026.

  • Leroy J. Blinn, Henry Carey Baird & Co., New York. Tin, Sheet-Iron and Copper-Plate Worker, new enlarged edition (1920). Supplied source, read as a subject map of the tinsmith's hollow ware: pans, dish kettles, pails, dippers, measures and wash-bowls cut from patterns and seamed, and the weights and expansion of metals. No text, patterns, tables or engravings are reproduced; this book's treatment of drawing and spinning such shapes from one blank, its examples and its figures are its own, in SI units.
  • ASTM International. ASTM A240/A240M Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications (Current edition). Named by number and scope only, as a specification under which 304 stainless steel sheet is commonly supplied. No values are quoted from it; the material properties used in this book's examples are illustrations, and a real design uses the supplier's certified properties.

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