I also went the route of the 3.2HP DC treadmill motor and KBMM controller with heatsink and fan because for less than $300.00 I was up and running, I can't do rigid taping and torque at 150RPM sucks.

Adding a tach signal (hall-sensor) to the motor allows mach3 to attempt to maintain the RPM but when I'm drilling with a 1-1/4in drill bit (after a pilot hole) the drill bit stops as the response delay in mach3 can't be avoided at such low RPMs.

Above 300RPM it's not so problematic maintaining a fairly constant RPM as the motor is starting to generate some power but it's still nothing close to the motor that dwalsh62 describes and I've seen it in action.

When my first treadmill motor failed, dwalsh62 made a new 3/4in output shaft and pressed the armature on it, a new front bearing retainer / front motor cover to hold the upgrade 6004-2RS front bearing and this custom/rebuilt motor has been running for almost 2 years now and better performance than when it had the shaft with the integrated helical gear cut into it.

The KBMM-225D controllers used to drive DC brushed motors wont provide torque at 0RPM unless the two I have are broken and came that way when I bought them new and they forgot to add the instructions to achieve this in the manual.

Prior to the KBMM I was using an ElectroCraft DC servo amplifier and a 600W 180V brushed DC servo motor with a 500ppr renco encoder I salvaged from a broken surplus canadian military telescope that I got off of ebay, this would give full torque at 0RPM and the driver was configured to use analog -10V to +10V so rigid taping and direction control were possible.

I'm known to be resourceful while I play like many here do and I also don't have the money to toss around buying stuff like the described motor and VFD but eventually I'll pick something up used when the opportunity arises that meets my budget (cheap) as I meander through posts looking at other peoples concepts and solutions.