Woodturning Blog: Articles, Tips & Ideas

M42 HSS: The Science

by Paul Carter | September 13, 2017

Steel is an amazing material. It comes in an array of types, from stainless to high speed. The distinct structure of each variety makes it optimal for different applications. M42 high speed steel has been used for centuries in shops of all kinds, from enormous factories to your personal woodturning shop.

M42 high speed steel has a unique structure, allowing its trademark durability and edge sharpness. A 10% additive of cobalt is responsible for M42's toughness. Cobalt allows heat-treatment up to 64-68 HRC. This provides M42 with outstanding edge durability. Furthermore, M42's composition is unusually tight, meaning it can be honed to a fine edge. 

In addition to a fine edge, it is the heat-treatment process that makes M42 the industry standard for hundreds of applications. 

Steel is shipped from suppliers to machine shops around the world in an annealed state. Because this is the steel's softest and most relaxed state, machining the steel in this form is much easier. Heat-treatment always takes place on annealed steel. Once a steel has been heat-treated, it can be returned to it's annealed state. Steel cannot be re-heat-treated without first being annealed.

Once the steel has been machined, it moves onto heat-treating. Different types or grades of steels can be heat-treated to different harnesses. Because M42 has a 10% cobalt content it can be heat-treated harder than most high speed steels, to 68 HRC.

After the hardening process, the steel is very brittle and pressured. This is why tempering is the next step. Tempering reduces the internal stress of the steel and increase robustness.

Once the steel has been tempered it is ready for use in a huge warehouse, machine shop or at your wood lathe.

Questions? Call our metallurgists at (206)878-7672. Happy turning.