Vertical upright, swing-arm and generator install 7 of 7.
After testing various spindle diameters and surface roughness I settled on a 5/8" diameter with a light knurled finish. With the spindle still spinning in the lathe I took off the sharp edges of the knurl with 220 grit wet and dry sandpaper.
As I mentioned earlier it is imperative that the motor shaft is not exposed to any side loading or trauma greater than you can apply with your fingers.
Thus I drilled the bore hole slightly undersized, then ran a 5/16"reamer through to get a nice round and perfectly sized hole. This gives a great fit but requires tapping the spindle into place which is unacceptable. To prevent this required and undesirable tapping, I over-sized the hole a few thousands by running a 5/16 drill through several times.
After this last operation the spindle can be installed with your fingers only.