Grinding is what's actually done. Most everybody refers to it as turning, but it's not the same as turning a rotor on a brake lathe, for example. A flywheel is properly resurfaced on a machine that has a large grinding stone that spins while the flywheel also spins, but off center of the stone, to achieve a non directional or "swirl" type finish. I've seen people chuck them up on a brake lathe before and do a real purdy job, but it's incorrect and will lead to clutch chatter and wear the clutch disc prematurely. But yes, technically flywheels are indeed ground. I've never said "I've gotta get my crankshaft ground", either, I've always called it "turned" but they are also ground of course.
