According to yourname :
Chris Lcan picture how cooling would prevent brittleness. I can't
imagine how
lubrication could prevent brittleness.

Mike's gotten confused. You don't use lubricants with grinding wheels.
Grinding wheels should be used on dry metal, they rely on both the
abrasion and instantaneous melting (the sparks) to cut. With hardened
steel or carbide, the melting does more of the cutting than the abrasion
does.

While you don't see it in the average shop, there are plenty of wet high
speed grinding processes. Full flood coolant on a surface grinder or
cylindrical grinder. Taking a part out to dip it in water is not a
production oriented process

I think it's save to omit high speed production grinding systems
from what a guy who can't afford to have a metal lathe - the
context of the original thread.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.