The spindle will not rotate at all. We can freely rotate the spindle by hand and see right rpm's. We have determined conclusively that the drive is good by swapping with another identical machine. Motor connections are good and the motor passes megger checks. Voltage is making it to the motor. We are now preparing to remove the spindle motor for diagnosis/repair/replacement.
I was looking at the drawing and noticed a "power lock" where the motor couples to the spindle shaft. This looks like it may require removing the spindle to get at the bolts to remove this power lock. Can anyone comment on spindle motor removal? There's actually a written comment on the drawing saying that all of the highlighted (most of the assembly) has to be removed to get the spindle out, so it is confusing. If most of the assembly (which includes the motor rotor!) has to be removed to get the spindle out and the spindle appears to have to be removed to uncouple the motor from the spindle shaft, I'd say this is going to be trouble.
See this pdf file for the page I'm talking about. Item 33 is a "power lock" and it looks like spindle side bolts have to be removed to get at it.