the problem is that they dont have a maximum speed. with no load you either need to turn down the voltage which causes heat, or they speed up until something fails. many good milldrills have a 3 phase motor and a small VFD now. cheap drill presses are cheap and they are not going to spend extra redesigning them. VFDs are getting cheaper and 3 phase motors only have bearings to wear out. the belt grinder for knife making at my space is a shop made tool, the only parts we had to buy were the pulleys and the VFD. its a couple hundred bucks all in and has lasted for atleast 6 years, other than bearings wearing out. the motor and frame parts were all free/junk.
