Three phase will run smooth and be better for machining. The Bridgeport motors are proprietary C-face motors. Any other motor single or three phase would have to have a mounting plate to fit the top housing.
A VFD is good if you get the right one and it replaces the switch on your machine plus you can have variable speed from the POT. A RPC will run the whole shop though and you must use the machines as they were designed.
decisions decisions...
