[QUOTE
Has anyone mounted the encoders on the shaft? I would think that would be better then the motor, in case the coupler breaks (just had that happen last night on my other machine). What happens when the motor gets the command to move, but it sees the shaft isn't moving?[/QUOTE]
I have my X encoder on the mill mounted on the shaft and has been working well for about 14 years! I had a belt break one time and because the motor turned and the shaft didn't, so it faulted out on an error!
You just have to make sure there is no backlash between the motor and shaft.
Art
AKA Country Bubba (Older Than Dirt)