Forging: design rules
Shaping hot or cold metal under pressure for strong parts with favourable grain flow.
Typical tolerance
Typical closed-die: about ±0.5–1 mm on forged surfaces; machine critical features.
Files to send
STEP of the finished part and a drawing with machined surfaces; the shop designs the forging die around it.
Common materials
Carbon and alloy steel, stainless, aluminium, titanium.
The rules, with reasons
- Draft. About 3–7° on closed-die forgings. Why: The part must come out of the die.
- Radii. Use generous fillets and corner radii. Why: Sharp corners cause cracks and fill poorly.
- Machining allowance. Plan about 1–3 mm of extra material on surfaces that will be machined. Why: Forged surfaces are rough and slightly scaled.
- Volume. Closed-die tooling needs volume; open-die forging suits large simple shapes in small numbers. Why: Die cost is the main driver.
- Grain flow. Tell the shop the main load direction. Why: Forging aligns grain with the shape, which adds strength.
Before you ask for a quote
- Material and grade
- Quantity
- Finished-part STEP and drawing
- Heat treatment and testing
- Certificates
Common mistakes
- Sharp corners
- No machining allowance
- Ordering closed-die forgings for a handful of parts
Request a quote Find manufacturers
Typical rules of thumb, not a guarantee. The manufacturer's own design guidelines override them: ask for them and check your design against both before ordering.