I live in a residential development, so there is no convenient 3-phase available. I borrowed a rotary phase converter for my initial playing with the lathe, but from the start I planned to use a VFD.
The Feeler, like the Hardinge original, has a 208V 3-phase, two-speed spindle motor that drives the spindle through a mechanical variable-speed transmission (that itself uses a 3-phase motor to adjust its ratio). The coolant motor is likewise 3-phase. The 110V control circuitry was fed from a stepdown transformer wired between two of the incoming phases.
After much online research into VFD's, I decided that the easiest course of action would be to simply use a VFD to synthesize 60Hz, 208V 3-phase from 220V 1-phase. The operation of the lathe would be unchanged as far as the controls were concerned.
I did read that the output of a VFD should never be switched, under pain of blowing output transistors etc. (akin to never unplugging a powered stepper motor, something I have unfortunately, though accidentally, experienced). The concession I made was to remove the handles from the forward/reverse and high/low spindle switches so I wouldn't accidentally actuate them.
Since I was bringing in 220V 1-phase, I could also bring in the neutral line and pull the 110V control voltage from one phase plus neutral. That eliminated the control transformer.
The three motors in the lathe add up to 2-5/24 HP (yup, that's what the nameplate says) so I bought a TECO FM50 3HP VFD, and a steel electrical cabinet to house it in, which I bolted to the right side of the lathe. I ran a piece of 3/4" steel conduit between the lathe's electrical cabinet and the new cabinet.
I wirenutted the new 4-conductor power cord into the input of the main contactor and tied the output of the contactor into the FM50's input terminals. I wired the VFD's output terminals back to the wiring bus to feed the three 3-phase motors. It worked, though it looked like a mad scientist's lashup...