[CarveOne]

Ron39,

I tried the plastic pulley and the diameter is about 1/8" smaller than the coupler. The stepper mounting bracket does not have enough range in the bolt slots to tighten the belt. A new bracket would have to be made so that there is enough length in the obround slot to allow proper tensioning of the belt.

The 1/2" x 1-1/8" bearings I used on the lead acme screws are slightly larger than the coupler and would probably fall within the adjustment slot range. I don't see a good way to provide washer "flanges" that rotate with the outer bearing ring. Stationary flanges would be easy, but I'm not sure that those wouldn't cause belt wear. Not sure that the belt wouldn't run off the bearings if there were no flanges. The 5/16" idler bolt would need a bushing to make it fit the 1/2" ID bearings.

Skimming off the surface of the coupler in my lathe so that it is true all the way across it would also cause the same problem as the smaller pulley.

I'll try skimming the coupler surface first, and only remove the minimum amount. If the stress from pressing in the bearings cause the coupler to split, I'll make up another one and remove a little of the coupler's ID so the bearings fit snugly but don't deform the outer surface of the coupler (It's nice to have a lathe and mill handy.) I only have one extra bearing at the moment but will order more spares later.

CarveOne