Unfortunately, grinding hard spots is only a temporary fix. As the drum (or flywheel) continues to wear, the hard spots become high spots again. A heat-hardened spot in a drum or flywheel is football-shaped, and the spot that shows up on the surface is like the tip of an iceberg. The only way I've been able to fix a hard-spotted flywheel is to machine the entire hard spot away, and that takes a really deep cut. Drums with hard spots are rarely salvageable, even if they're ground smooth.
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!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!