I have the 3 phase Leeson motor hooked up to the Teco L510 VFD. It is running strong. I suggest this modig=fication even if you do not intend to convert to CNC. You can hook up a potentiometer to control the speed from the panel or just adjust it at the VFD. I have the stand offs turned. Now I just need to machine the mounts for the steppers and ball screws.
I cast the refractory and cured my new furnace. So far I have < $150 in my entire casting setup. The biggest cost was the Bentonite Clay, mold starter kit, and Crucibles I purchased. I hope to be melting metal next week.