You can surface grind them there are techniques like using half magnet or less than half magnet to grind the first side, by doing this you eliminate the spring when you release it, whack it over then do the other side, I tend to use half magnet on anything I grind though, you should be able to move the part on the magnetic table with your hand, then you know it's clamped enough, although it's fun when the wheel explodes in your face, hahaha.
You actually managed to get an aztec rotor :- only the best.
Phil.