High Speed Steel generally contains large amounts of Alloys such as molybdenum, chromium, tungsten, vanadium, and cobalt with sufficient carbon to provide excess alloy carbides in the final heat treated structure. These grades can easily be hardened to a range of 64 – 70 Rockwell “C”. Maximum hardness is attained through secondary hardening after tempering. Aside from its hardness, one of the most important characteristics of high speed steel is its ability to retain this high degree of hardness at elevated temperature.

High Speed Grades

M-1: One of the earliest and most simple of the high molybdenum HSS. It has an exceptional balance of toughness, wear resistance, and red hardness. It is especially suitable for a large variety of cutting tools. It is readily machinable, hardens uniformly to a high hardness, and possesses excellent cutting qualities. While it is possible to obtain high levels of hardness, its relative toughness is nearly equal to that of M-2. “HSS” is used for making drills that will be used in a wide variety of applications. M-1 has some of the increased red-hardness properties of M-2, is less susceptible to shock, and has “flex” capabilities generally favored for general purpose work.

M-2: Is a high molybdenum HSS that has also been a standard for a number of years. It has extremely high toughness coupled with good hardness, wear resistance and red hardness. Its balance of properties lends itself to a wide and diverse range of applications from taps and general cutting tools to dies, rolls, punches, and other general purpose tools. “HSS” is the standard material for HSS cutting tools. M-2 has good red-hardness and retains its cutting edge longer than other general purpose high speed steels, not as shock resistant or as flexible as other HSS grades with less tungsten. Generally favored for high production machine work.

M-7: Is a modified molybdenum high speed steel containing more carbon and vanadium than grades M-1 and M-2, and includes a small addition of nitrogen. This makes it possible for M-7 to attain a greater hardness and faster heat treat response. It is ideally suited for special cutting tools where wear resistance and red hardness are required for maximum cutting efficiency. “HSS” is used for making heavier construction drills that can be used for portable drilling of hard sheet metal alloys. Generally favored for work in Aircraft plants where flexibility and extended drill life are equally important.

M-35: “5%” COBALT is only used for making tool bits. It has some of the increased red-hardness properties of M-42, and is not quite so susceptible to shock.

M-42: Is a high cobalt steel that finishes to a very high red hardness and has excellent cutting hardness. Due to its lower vanadium content, the grindability is relatively good in spite of the high hardness levels which can generally be obtained. Because of its unique combination of properties, this grade has gained broad acceptance in the aerospace industry for machining superalloys and other difficult high strength alloy compositions. “SUPER COBALT” is the standard material used for all cobalt cutting tools. It has excellent resistance to abrasion and very good red-hardness for working difficult materials.

M-50: Is an intermediate type high speed steel of the molybdenum-chromium, vanadium variety. M-50 is recommended for applications involving moderate cutting conditions, such as wood working tools where toughness properties are most important and there is less of a need for red-hardness than is typical of standard high speed steel. “HSS” is used for making drills that will be used for portable drilling and where breakage is a problem due to flexing the drill. Does not have the red-hardness of other grades of HSS with tungsten. Generally favored for Hardware and Contractor use, although they are also sold for industrial uses.

TOOL DATA: Reference and Documentation

Tungsten – Note

Generally speaking, a cutting tool made of high speed steel containing the element tungsten will possess the very desirable property of “red-hardness”. This enables tools to cut at a dull red heat (up to 1000 degrees F) without loss of hardness or rapid dulling of cutting edge. Cobalt high speed steel will exhibit even greater red-hardness and wear resistance.

Super HSS – Note

The term “SUPER HSS” is not definitive and can mean almost anything that one wants it to mean from ordinary M-50 to High Cobalt material.