Jim Gott wrote:

My machinist friends don't support the "you can't hurt HSS by
overheating" philosophy. They agree it is much less prone to damage but
recommend you learn to grind without bluing.
Billh BRBR

A member of our AAW chapter is a metallurgist, and he explained to us that
bluing will NOT make a HSS tool lose its temper. I don't recall the
temperature that makes steel turn blue, but he said that HSS is tempered
much higher than that. You would have to heat it to "straw color" to take
away the temperature, and an aluminum oxide wheel is not capable of
getting HSS to the "straw" stage. Carbon steel tools are the only tools
you can't blue without losing the temper.

I think you've either misremembered or misunderstood something he said.
Straw color is about 425F, blue is 600 for carbon steel. For other steel
formulations the color vs temperature scale changes, but straw is always
cooler than blue.

M2 is typically drawn at 1000F, which is a faint dull red glow, just barely
visible in sunlight, so just getting it blue shouldn't have much effect on
the temper.

-Jim Gott-
San Jose, CA

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)