i have a mandrel that fits a lathe, having a register the exact size of the axle/hub factory register. it is also the diameter [actually a little larger] of the hub/axle the wheel bolts to, so that the drum [or rotor] being turned is retained as it would be with the wheel bolted to it.
as a machinist, i feel this gives a better result than the parts store "cone shaped" locating device that just picks up the center hole of the drum/rotor being turned.
i also use a much larger cutting tool, which not only gives a much better surface finish, [being a substantially more rigid tool] it also doesn't "bounce around" like the tiny [in my opinion] cutting tools used with the parts store machines, thus giving a much truer diameter to the finished drum and a much flatter surface to the finished rotor.