AC Servo question

Lathe and milling machine spindle control is a great feature for these CNC
conversions but the power requirements to run a 1 or 2 HP spindle makes a
stepper or DC servo a big expensive beast.

There are now AC drives for 3 phase motors availible in the $200-$300 range
with a pretty good speed range. Surplus 3 phase motors are cheap or may
already be on your machine.

Any clue if these have the response and low speed torque needed to slave a
spindle to a lathe carrige to do threading?

https://store.plcdirect.com has for instance a Hitachi SJ100 Micro drive:

"Micro drive, 1 HP, single/three phase input, three phase output, 230V,
sensorless vector or VF control modes"

for $250.