This specification covers seven tungsten-type (types T1, T2, T4, T5, T6, T8, and T15) and nineteen molybdenum-type high-speed steels (types M1, M2, M3, M4, M6, M7, M10, M30, M33, M34, M36, M41, M42, M43, M44, M46, M47, M48, and M62) in the form of annealed, hot-rolled bars, forgings, plate, sheet, or strip, and annealed, cold-finished bars or forgings used primarily in the fabrication of tools. Two intermediate high speed tool steels designated as M50 and M52 are also covered. Unless otherwise specified, material shall be made by an electric melting process. A chemical analysis of each heat of steel shall be made to determine the percentage of the elements specified (including carbon, manganese, phosphorus, sulfur, silicon, chromium, vanadium, tungsten, molybdenum, and cobalt) and these values shall conform to the requirements as to the prescribed chemical composition. Requirements for: (1) heat treatment such as austenitizing, quenching, and tempering, (2) hardness testing (3) macrostructure and macroetch standard for porosity and ingot pattern, and (4) decarburization determination are detailed. The maximum Brinell hardness and minimum Rockwell C hardness for the tool steels are given.