REX M42 is a high-speed steel that can be heat treated to 68 Rockwell C hardness. Its higher hardness makes it outstanding for special-cutting tools with requirements beyond the capability of general-purpose high-speed steels. CPM REX M42, produced by the Crucible Particle Metallurgy Process, is an improved quality product with homogeneous macro and micro sections exhibiting a finer grain size, better toughness and superior grindability in the heat-treated condition than conventionally produced M42. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on forming, heat treating, and machining. Filing Code: TS-438. Producer or source: Crucible Specialty Metals Division, Colt Industries.