Ah, Muzzer, ask why though. It was to have an accuracy in positional control on the spindle position for threading. Oversized to avoid pulleys - yup, that's the rationale behind replacing a 350W motor with a 2kW motor. The servo is driver by step/dir exactly for positional control, via a 1:1 pulley direct to the spindle.

Cost, actually, not substantially different to the 3 phase 4 pole motor with VFD that I replaced with less than 12 months on it, to be honest. And I don't have the lag through the VFD for spindle speed.

Oh, and another reason - because it's an interesting experiment if nothing else.