Tool steel materials are some of the most highly hardenable materials to be heat treated.  While this characteristic is useful in the final application of these parts, there are accompanying precautions in heat treatment that must be learned for specific parts to successfully produce the high hardness without distortion or cracking.

 The most common tool steels are the oil hardening series, air hardening series, and high speed steels.  The single applicable heat treatment is hardening and temper, which may be performed in atmosphere batch furnaces and in vacuum furnaces.  Cryogenic treatment has been found to enhance tool steel life by extracting additional hardness from the heat treatment processes.  Tool steels treated in atmosphere my require glass bead finishing, while those bright hardened in vacuum will usually not need further surface cleaning.