You're aware that most VFDs when fed from single phase power must be
derated
to 75%?


On older VFD's this is generally true, but almost all of the new VFD's rated
for 3 HP or less are designed to run full output power with only single
phase input power.

Also, I agree with Gunner, yank out the mechanical vari-speed drive and run
the motor direct using the VFD for speed control. I did this on my Clausing
5914 and it works great. You need to pick your motor pulley size carefully-
I picked mine so that when the motor is double speed the lathe is at its top
rated spindle speed.
By the way, this is a real easy conversion to do on a 5914 since the spindle
already has a toothed belt pulley on it- make a new motor plate, use the
existing motor plate brackets moved up to the upper slots, buy a new motor
pulley and belt and you're done.

You don't get full HP at lower spindle speeds, but you don't have the losses
(and noise) from the mechanical vari-speed anymore (which aren't small) so
power generally won't be an issue.

Good luck-

Paul T.