Re: [CAD_CAM_EDM_DRO] Milling HSS

> IMHO HSS only gets a bit softer from annealing, even a carbide tipped
> cutter would struggle.you would have more luck milling annealed tool steel
> and hardening after. Isometimes turn the shank of a drill with a carbide tip
> at work but have you got a carbide tip mill cutter? You could try annealing
> a bit and try a file on it, if you cant mark it its probably too hard to
> mill.
> Chris Paine UK

I finally found some info on annealing M42. ( 820-870 C ) (1508 - 1598 F) then cool very slowly. i.e 11 C / hr. this is supposed to
give a hardness of < 286 HB. Not bad considering the hardness/toughness you started with. Apparently the trick is not to
overheat...just get it austenized then cool slowly....do not get so hot that you convert all the alloying components to carbides.
The hard part is the slow cool and I suspect that is where most people have problems.

Dave