Engineering Reference

Thread rolling

Forming a thread by displacing material between dies rather than cutting it away.

Definition

Rolled threads are formed, not cut, so the grain flow follows the thread profile instead of being severed by it. That makes a rolled thread roughly 20 to 30% stronger in fatigue than a cut one of the same size, and it leaves no chips.

The blank diameter is not the nominal diameter — it is approximately the pitch diameter, because the material has to flow up into the crests. Using nominal-diameter stock produces an oversized thread.

Common misuse

Turning a thread blank to nominal diameter before rolling. It makes the finished thread too large; the blank should be near pitch diameter.

Related