I do not believe there are any specs involved. What you want to accomplish is to get all the grooves out and still end up with enough "Drum wall" to dissipate the heat . More brake pureists may chime in and discredit what I believe.
I totally agree with you but out here in Cali..."the land of fruits and nuts" it's illegal for a shop to turn an out of spec drum. So unless you can do it yourself your screwed!!!
Not just California, all 50 states. I suppose that some of the shadier "mechanics" might turn a drum (or rotor for that matter) beyond the specs just to make a buck, but those of us that actually take pride in our work know better.
