I dug out the capacitor last night... it's a 23600 uf electrolytic that can handle 40 volts. Should be ok for this use.
I'm building a basic power supply as detailed on this web site:
Step 25: Power Supply Part 1
I've collected all the parts although I need to de-solder the bridge from the circuit board it's on. Probably I will assemble things like it shows on that site, just wiring them together on a board. I'd like to have a circuit board for this but I haven't been set up to make one of those in years. Maybe I should buy some perfboard or something, but most of the components won't mount on the board anyway.
I ordered timing pulleys and belts for the steppers. I'm going with about a 4:1 reduction, so it'll be slow, but I'm hoping that lets the steppers deliver the torque needed to operate the acme screws. XL belts, I ordered 3 sizes so I'd have the one I needed and I wouldn't get stuck on that.
On the down side, I dropped my treadmill motor while clearing some desk space last night to work on soldering, and snapped the tach disk off. Guess I'll need to make a new one. Probably I should mount the tach on the lathe spindle anyway.
I picked up some bearings to mount a jackshaft on for the motor at a local surplus place. Of course nothing fits exactly, including the shaft I was going to use, so I need to set the lathe back up far enough to turn some bushings or turn a new shaft. Once the jackshaft is mounted I'll drive it with a 3:1 pulley reduction (it's a 6500 RPM motor) and that will drive the lathe's gearing using the original drive belt. I also need to figure out a base/mounting for the whole thing so the new motor isn't just clamped to the bench behind the lathe, and I am hoping to flood cool the whole thing, so I need a better pan under it. Maybe I'll build one with MDF, I'll see. Wish I had a sheet metal brake.