After spending way too much time debating whether I should try this or not I have pulled the trigger on building my own 4th axis for my 1100M. So far I have acquired a stepper driver (SteppersOnline equivalent to the Tormach piece), a NEMA 23 frame stepper, BS-0 dividing head, and the appropriate CPC connector to plug it into the existing outlet on the machine cabinet.

Pictures and specifics of the build to come as I make progress but so far I have managed to get the stepper wired and responding to A-axis inputs from pathpilot without too much trouble. Unfortunately my stepper didn't last long before it started making a pretty awful noise (steady, high pitched beep sound) whenever the machine is taken out of reset. This didn't happen immediately but rather after 10-15 minutes of messing around trying to find a microstep setting that would work for the built in scale factor and the 40:1 head that I have. Not knowing what I could have done wrong but thinking perhaps I fried the stepper or the driver, I grabbed another motor I had laying around and plugged it in. This one was a NEMA 17 and rated for less current than the original. Within about 5 minutes it started smoking and making the same noise. Given the behavior, the reduced time to failure for the smaller motor, and the resulting notchiness of both motors (more so than before they were plugged in), I believe the motors were not capable of handling the current output from the drive. The NEMA 23 was rated for 2.4 amps which was within the range of the driver at the lowest setting but less than that setting's maximum output. The 17 was only rated for 1.something so it makes sense that it would burn up faster. I now have a 4amp stepper on it's way so I can run it at the drive's lowest setting and have some overhead available. Assuming I'm right about the cause of failure, that should solve the problem. It does look like I will have to alter the scale factor in the machine settings file which is a bit annoying but doable for now.

In the meantime I am working out a mounting solution and drive coupler for the stepper to the dividing head. Nothing terribly complex but one that will allow for easy access to the worm gear adjustment lock screw so I don't have to tear everything apart to tighten up any backlash.