How to use AC motor with axis?

As a follow up, I opened up one of these drives this week: 

I thought the forward/reverse lever was just a switch, but on this model, they are also a lever that engages the motor shaft with the small bevel gear.
(i.e. the clutch, so that you can manually turn the mill axis handle without driving the power feed motor as well.)

This means effectively the forward & reverse is electrical, but the on/off is both mechanical and electrical.

Not easy to interface to - would need to mechanically lock the direction lever in one direction, and then override all the electronics to get fwd/rev.
Possible, but not worth the time. Removing/selling the power drives, and adding steppers, will be much faster/easier

If you wanted to retain hand control, you could consider adding an electric clutch that was activated released with 24 V power. I seriously considered this using some old clutches salvaged out of a photocopier..