Most 3/4 ton drums can go .090" oversize without problems, but don't take any more out than necessary to clean up the majority of the roughness. A couple of grooves in a drum with most of it smooth and round will not cause major problems. The old style riveted-on brake linings used to cause a couple of deep grooves where the rivets started contacting the drums without causing other problems. I've turned many drums mostly smooth while leaving a groove or two. No problems with those drums.
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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