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Casting Shrinkage

Metal shrinks as it solidifies and cools, so the pattern must be made oversize by the alloy's shrinkage allowance (the “patternmaker's shrink”). Get it wrong and every casting is undersize.

Finished dimension (mm)

Alloy

Override shrink (%) — 0 to use alloy

Shrink allowance

—

Pattern dimension

—

Added material

—

Linear allowance only. Thick sections, cores and constrained features shrink differently — a foundry will adjust from experience.

A helper, not a substitute for engineering judgment. Verify against the governing standard.