Engineering Reference

Hard turning

Turning hardened steel with a very hard tool instead of grinding it.

Definition

Hard turning replaces a grinding operation with a single-point cut in the hardened state. It needs ceramic or CBN tooling and a rigid machine, and it can hold tolerances and finishes that rival grinding.

The economics decide it: hard turning is faster and more flexible for complex geometry, but it does not correct distortion the way grinding does, and it can leave a different residual stress pattern on the surface.

Common misuse

Hard turning a part that has distorted in heat treatment. Turning cannot correct the distortion; grinding can, which is often why grinding is specified.

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