The overall design of the belt drive:
I'm planning to attach to the top of the upper spindle housing for the spindle pulley. There is a pretty decent chunk of material to grab onto on this mill. I'll set 6 grub screws around the perimeter and dimple the spindle housing in all six positions by about 0.065". I'm hoping that will allow the pulley to be secured such that lateral force will not tend to wobble it off. Option B would be some way to grab the spindle splines and do away with the attachment to the upper spindle housing if plan A proves not to work.
Machining the pulley blank:
1.) 3.5" Solid Stock squared up on the lathe. This was a bit too much for the metal chop saw I bought this summer from Northern Tool too replace my abrasive saw that finally died. I had to make about 40% of the cut, rotate 90 degrees and make the remainder of the cut. That left some rather poor ends that needed a lot of facing to clean up.
2.) Machine the final diameter of the collar that will house the grub screws that grip the motor shaft. 1200 RPM and 0.050" DOC, 0.050" per rev with a CCMT insert had streams of chips flying off the stock. Still took a good number of passes to reduce that diameter to 1".
3.) Machine the rough dimensions of the pulley steps. 3.4" and 2.13"
4.) Grind up a tool bit for the 40* angle of the micro-v ribs on a poly-v belt. I'll be using a 4 rib belt "J section". Belt is about 3/8" wide and 18.625" in circumference. I lucked out on my design because the middle position of the adjustment in the motor plate creates an ~18.8" circumference. That was the smallest belt in that profile McMaster offered. Tested the tool out and it seems to do a decent job on the grooves. My grinding skills suck and cobalt tools take FOREVER to grind when start creating a significant length of cut. I am wishing I had made the belt channel a bit wider. Clearance may be a problem on the right-hand side of the pulley channel as it stands.
I'll wait for the belt to arrive to test the fit in the grooves before I finalize the motor pulley.