Bearings. It turns out I could not find 40 degree angular contact bearings that have rubber seals, anywhere. So I went with radial ball bearings with rubber seals after the SKF engineer told me that their line of 6200 series bearings have an axial load rating that is 50% of the radial load rating. I was surprised that it was that high, but happy. That makes these bearings relatively cheap since they are so common. Higher cost bearings are usually higher rpm and have increased clearances and special low expansion balls for the higher rpm he told me. These bearings are 6209-2rs1. They are 45mm id x 85mm od x 19mm thick. So far my rpm limit if I was lucky will be 1000 rpm. More likely 300-400rpm. I have to do some testing of these servomotors for top speed to see how they will do. Maybe I can back calculate the rpm since I use the same motors for the cnc mill. If usps is any help, the bearings should arrive this Saturday. That way I can see how well they fit the od of the 5c spindle.
Thinking out loud. 135ipm. 20,000 pulses per rev. 20 turns per inch. Hmmm. 135ipm x 20 turns/inch = 2700 turns per minute or 2700 rpm. Hmmm. Much higher than I thought. And that 2700 rpm is at the motor while moving a heaving table and long ball screws. Although there is no cutting load. The limit for rpm so far is the pulse train out of the parallel port. My break out board is only 3 axis output. I'll need something more complex for this project. With a 5:1 belt reduction, 2700rpm becomes only 540 rpm at the spindle. 3:1 the rpm is 900. I don't think I turn more than about 400rpm on my lathe anyway. I'll double check that. Anyway, the rpm at the spindle with steep reduction I plan is slow. But the first project will be cutting delrin. So high rpm is not a requirement. There should be enough movement in the motor mounting to allow several different pulley sizes.
I tried fitting some 5c collets to the spindle last night. Not much success at first. The indexing pin was far too tall. So I reached in with a dremel and knocked it down some then deburred it the best I could. After some more fiddling it tightly fits a 5c collet now. The id of the spindle is the collet area seems to need some smoothing with scotchbrite or equivalent.
Just added the 5c collet knob and tube shaft. The knob was easy to design. I took the main diameter furnished with the indexer then subtracted 6 1" diameter rods inset just .125". This gives a nice gripping feature to the knob. But without super sharp edges. I'll had a hole for using a lever for added tightening as I have seen in the past.