George, you're a metals or materials guy, and you talk sense, e.g. "If there are residual stresses in the disks, machining = stress relief >>>>----> warpage, among other things."

Could you please explain WHY a good shop in our neighborhood, for instance, persists in machining rotors whenever they change brake pads? Results: my buddy, recently, driving his Toyota van from MN to Ohio, has his front end fail in the middle of nowhere. Why? A brake rotor had fractured at the "hat." (Good Samaritans appeared, and all was eventually put right.} His brother, a brakes M.E. guy at Delphi, if I get it right, thought that the shop had probably hammered on the rotor to remove it a few weeks ago, when pads were replaced. (Cast iron doesn't like this, does it?)

WHAT would it take to convince shops NOT to use this resurfacing/grinding technique, AND to inform consumers of its irrelevance?

Was it ever necessary or beneficial?

Thanks!

P.S. This costly abu$e of brake rotors is what led me to start taking care of our cars myself, about 5-6 years ago. What was it, about $300 and a day wasted, when my wife's Corolla needed new front pads? (I didn't know how to disable the pad's too-thin noise-maker. She was in a hurry to go home because her dad was dying.) Last Easter, on the other hand, I replaced the pads before church. :-)