Even grinding the hot spots doesn't soften them, so the problem just reappears in a short time. Hot spots are actually football-shaped, so the small area that shows up as a hard, high spot that a tungsten carbide bit won't cut during drum-turning operations will require a great deal of machining to eliminate it altogether. I've encountered the same problem during flywheel grinding when doing a clutch job.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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