The key word is high speed steel. A2 is not HSS, M2 is and as far as I know
Sorby doesn't offer M2 tools. Tempering temps for A2 range from 350 to 1000
degrees. M2 tempering temps are well above 1000 degrees; I think they are
around 1700 degrees. So no you won't soften M2 but you will soften A2 at
the edge. Straw-yellow color in tool steel occurs at 460 degrees, blue at
560 degrees well into the range to soften A2. You may have confused what
your friend was saying. If he was talking about hardening A2 then yes the
temp would be around 1700 degrees but for tempering (which is actually
softening the steel again) the temps are much lower. In a very general
sense, the higher the tempering temperature the softer you make the steel.

All temps are in Fahrenheit

"Jim Gott" wrote in message
...
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.
-Jim Gott-
San Jose, CA