Part of my planned conversion is a swap of the BLDC spindle motor to enable control of the motor via the controller interface.
The servos that I bought in the kit are DMM so I looked at a DMM 1.8 HP AC servo and driver. North of $1000 USD is too expensive for my blood.
I can get a no-name AC servo and driver off eBay for about $750 CDN which is a
bit more palatable but still expensive. And the sketchy documentation, tuning software is not great.
I considered an AC motor and VFD but the motors in the 1.5 HP range are heavy beasts and I'm not keen on putting that much weight on the head of my bench mill.
Ran across a lathe CNC conversion that used a 90V DC treadmill motor with a KBB driver that uses a potentiometer to control speed. The conversion I saw used a board to take a PWM signal from the CNC controller as input to the KBB driver board allowing full control of rpm and direction of the DC motor.
KBB board:
www.emotorsdirect.ca
PWM control board: