You may have seen articles in the past few months describing methods for achieving a better surface finish or "Ra" value on turned rotors. Perhaps one of the easiest ways, provided your lathe is in good shape, is to use a good quality brake bit. Figure 1 shows a new bit that is producing better results on lathes to which it is applicable. In a properly operating lathe, it allows you to use a higher rate of speed to turn rotors and achieve a smoother finish.
Figure 2 shows a magnified view of average rough and smooth finishes on brake-rotor surfaces. Something as simple as changing the lathe bit will greatly reduce the time spent on a brake job by enabling you to achieve a smoother rotor finish at a higher spindle speed. In fact, when properly set up and used, bits such as the one shown and some other designs allow you to achieve a finish so smooth that a non-directional finish is not needed after turning. You simply wash the rotor and reinstall it. Time studies have shown that you can save half an hour on each job.