Finally found time to work on this machine.
I built a new controller using a Gecko G540 with a 48V power supply. I've still no idea what the inductance of the motor is but it runs well with no overheating. In trying to track down an annoying roughness (motor tuning was to blame), I found a couple of mechanical issues with the X and Y axis bearings. Nice and tight on the ballscrew but loose in the endplates. The motor end of the ball screw has a single bearing and the other end, two bearings. None seem to be angular contact type. Lacking a working mill, I'm going to put a shim around the bearing to make it a tighter fit. I'll check out the options for fitting better (angular contact) bearings to the existing end plates if possible.