my next project is my Hurco km3p. i currently have 2 of these, one running with original control and the other with a problem booting up. i am thinking about using ac servos from Mach Motion, along with Mach3 for the control. i would like to increase the spindle top end rpm. does anyone have any experience with building a faster spindle?
Since you sound like you plan to gut the machine already...
I saw a conversion offered at last years WESTEC tool show in Los Angeles.
It replaced the Vari-drive pulleys in the head with a single large timing belt and toothed pulleys and fit a good 5HP Inverter rated motor with mated VFD. It could be run off 220VAC 1ph power. They had bolt on kits for most popular brands. The KM3/KM3p is a Kondia/Clausing head. The VFD was a rather high resolution vector drive - and with a encoder fitted had proven well adapted for rigid tapping.
If I remember correctly it would allow you to overdrive the motor to a 6000rpm spindle speed. - Just understand that there is a bearing heat build up and thermal growth issues running that high for any extended time. Also going above the standard motor frequency causes both HP and torque to drop off.