We do replace more than we machine. We have went round and round on this subject. My former service manager wanted to machine every rotor. My new service manager believes we should be replacing instead of machining. My former service manager thought that by machining we would replace more rotors because the rotors would then require it for subsequent work. This is a situation where I see both sides. It is hard to do brakes and reuse the rotors if they are not machined due to pullsation, rust rings that cause noise and lips on rotors. However, if they are machined they are more subject to coming back quicker with pullsation issues. Machining may save money to the customer up front but cost more in the long run. Brakes lathes aren't cheap, require service, need lathe bits, silencer belts, etc. and take time to set up and operate besides they create a lot of dust.