Relief angle

Another name for the clearance angle — the angle ground on the flank to prevent rubbing.

Definition

Relief and clearance mean the same thing, and both terms appear in tooling catalogues. Where catalogues distinguish them, relief is the primary flank angle and clearance is the secondary one, but in most usage they are interchangeable.

The term survives mostly because older British and American texts used "relief" while ISO standardised on "clearance". Seeing both in one document is normal and does not indicate two different features.

Common misuse

Treating relief and clearance as different features and specifying both, which produces a contradictory tool drawing.