Al, I did something similar last year to paint my new wood wheels from Stutzman with a HVLP gun. I used 5/8 inch diameter 1045 bar and turned 8 inches of threads on one end of each bar for the hub. I cut the shafts to length, milled a flat and used a coupling to mount to the motor on the other end. Since I wanted to leave the bearing races in the hubs, I purchased rubber stoppers that were the appropriate diameter to fit in the race from each side. After punching holes in the stoppers, I used washers and a 7/16 nut on each side of the hub so I could squeeze the stoppers to hold the wheel on the shaft. This worked well and the wheel did not spin on the shaft. I found a double shafted, high torque motor on Amazon so I could use one motor for 2 wheels. I wanted to use 12V so I wouldn’t have as much risk of a spark when painting. I was unsure what speed would work and guessed at 5 RPM which was OK but I would have preferred it be a little slower. They had various speeds available and now I would use the 3 RPM if I was buying them again. The motor has a gearbox and they gave specs for the torque which I calculated would work for my weight of wheels. The motor I used from Amazon was: “uxcell Double Shaft Worm Gear Motor DC 12V 5RPM High Torque Speed Reduction Motor with Metal Gearbox”. I used pillow blocks to support the shafts on a wood frame which was mounted to my work stands. I found it was a fun project to build and I am planning to use them again when I have Stutzman make another set of wheels for my other car.