[Gdeaver]

The max velocity of the vertical shaft can be > 1200 RPM and while the load is with in tolerance of bronze thrust washers, the ball thrust washers are lower friction. We have yet to see any signs of wear with the ball thrust bearings. Our design pushed us to needle bearings for the vertical drive shaft. They also have provided a low cost durable solution. My only complaint with the needle bearings Is the shaft. Because the needles run on the shaft, the shaft needs to have good surface hardness. I would prefer a case hardened precision shaft. How do you cut a key way in a case hardened shaft? You don't. You can grind one. To avoid the time and hassle we use a 4140/4142 steel shaft. Rockwell B90. After a season there is some wear but very tolerable. We have used Igus bushings for many apps and they have worked very well If you follow Igus design guide lines. The hex shaft on the vex miter gears do not fit our current design and I would not change for them.