I just hit it with a grinder to take off the excess casting that rubs the caliper piston seals.
It was such a small amount, took all of a minute, no negative impacts.
Let me get this straight. When you say "hit it with a grinder", what does that really mean? Are you turning the rotor while you grind away with a hand held grinder? How do you maintain consistency that way? Sorry, but it sounds sloppy to me.