Here is what usually happens in our shop. The car is in the lube bay and they notice the brakes are worn under 4 mm. The writer sells the job with rotors because they don't trust the lube guys ability to judge the condition of the rotors. I don't machine a lot of rotors anymore maybe 1 or 2 sets a week. I look at it this way they only pay me 1.8 to machine rotors,replace pads,and service the arbors and pins. The pay me 1.5 to replace the rotors,pads and service the arbors and pins So is it worth it for me to set up the lathe and machine some rusted rotors for 0.3 ?

Gus