How to Heat Treat CPM M4
CPM M4 is popular in competition cutting blades as it is high-speed steel exhibiting better grit and wear resistance than M2 or M3 in cold work punches, die inserts and cutting applications.
While it may chew up belts grinding it after hardening, its exceptional edge retention and strength make it impossible to ignore and worth the inconvenience. If you are used to hard-to-grind and polish steels, you will be prepared to work with M4.