Question, how would you find the RPM's at the chuck so you know what speed its turning?
Pulley diameters determine RPM, so it would be necessary to do a little math. The motor turns at 1725 RPM, so you'd need to measure the diameter of the pulley at the motor, and calculate the speed change up or down for the idler, then do the same thing for the spindle pulley. It would give a good calculator a workout to get specific chuck speeds. I just sort of eyeball the speed of the drill bit, sanding drum, milling cutter, or other accessory, and adjust the speed up or down for the best cutting speed. Generally, the bigger the hole, the slower the speed needs to be. Milling cutters have a fairly narrow speed range where they cut effectively, and it's important not to overdo it on the depth of cut. I'd rather make several shallow cuts with a fast-turning cutter than try to hog out a big cut at low speed in one pass. It's also important to have the workpiece clamped down securely. Getting launched across the shop can do some nasty things to a project!
Jerry
