The sheet you choose decides how much force the job needs, how tight a radius it can take, how much it springs back, and how long the tooling lasts. Picking material is not a separate step from die design — it constrains every calculation that follows.
The central tension is strength versus formability. Stronger material resists deformation (good for the finished part) but is harder to form (worse for the process). Most selection is finding the material that meets the part’s strength and corrosion needs while still forming reliably.
Yield strength is where the material starts to deform permanently — lower yield means easier forming and less springback. Tensile (ultimate) strength sets cutting force and the wall stress a draw can survive. The gap between them, plus elongation, describes how much the material can stretch before it tears.
Work hardening (the rate the material strengthens as it deforms) affects multi-stage forming and whether you need an anneal between draws. Hardness correlates roughly with strength and is a quick incoming check; the Hardness Chart relates the common scales.
Rolled sheet is directional. Bending across the grain (bend line perpendicular to the rolling direction) is more forgiving and allows a tighter radius; bending along the grain is more likely to crack. Where a part allows, orient bends across the grain — and on parts with bends in two directions, that orientation is a layout decision.
Directional properties also drive earing in deep drawing. Material with lower planar anisotropy ears less. Grain direction is a real constraint on blank orientation and nesting, not just a material spec.
Thickness drives force (cutting force scales with thickness; bending tonnage with thickness squared) and sets the practical minimum bend radius — often expressed as a multiple of thickness that grows with material strength. The Min Bend Radius tool estimates that limit, and Bend Allowance turns thickness and radius into flat-pattern length.
Mind incoming thickness tolerance: real coil varies within a band, and that variation shifts tonnage, clearance behavior, and formed dimensions. Tight-tolerance work may justify specifying a closer thickness band.
Low-carbon (mild) steels form easily and are the default for general stamping. Stainless adds corrosion resistance and strength but needs more force, springs back more, and work-hardens aggressively. Aluminum alloys are light and form at far lower tonnage but are less forgiving on tight radii and more notch-sensitive. The right family follows from the part’s service and the process’s limits together.
List the part’s non-negotiables (strength, corrosion, weight, finish), then check formability: can the chosen material take the radii, draws, and bends without cracking, at a tonnage the press can supply? Use Sheet Weight and Material Cost to weigh the economics. The property generalizations here are typical, not exact — confirm against certified material data and tryout before committing.
sheet_weight calculator · material_cost calculator · min_radius calculator · bend_allowance calculator · hardness calculator