Resurrected old thread, ball spec.
I called Craig at Paradise Wheels. Looks like I did a big no-no. I bought balls from McMaster which are Grade 25 and also hardened to Rockwell 'C' of about 65. The grade 25 has much too loose a diameter tolerance. The balls also need to be Grade 5 or better. Paradise Wheels goes even better than that and uses Swiss made Grade 0.
The balls are supposed to be sacrificial and be relatively soft to conform to the races. The harder balls will scratch up the races and possibly the output shaft.