The indexer is working beautifully, controlled by a little arduino. After 25 revolutions (625 of the stepper) the mark lines up. There appears to be zero backlash, I will need to confirm that. Next step is to mount a 36 inch disc in the nova chuck and then perform the same test. On low resolution setting of 500 each pulse sent to the stepper results in a rotation of 0.0072 degrees, and on 1000 results in 0.0036 degrees. This is all before alpha stepping. I expect it will perform better with the shopbot control and software. Can't wait to make some sawdust with this thing...