Abstract AISI Type M4 is a high-hardenability tool steel developed to provide the excellent abrasion resistance that results from higher-than-normal carbon and vanadium in the molybdenum-tungsten high-speed steels. It is recommended where sharp edges are needed for fine cuts. It is an excellent choice for heavy-duty cutting operations and should always be used at or near its maximum secondary hardness. Typical applications are reamers, milling cutters, punches and lathe tools. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on forming, heat treating, machining, and joining. Filing Code: TS-376. Producer or source: Tool steel mills.