Ball turning tool
Block and Shaft
Click to enlarge pictures.
The block and shaft are the most important components for a good functioning ball cutter. These should be made so that the shaft fits perfectly in the block. In order to make this in an easy manner the opening in the block is made larger and there is a bushing pressed on both sides into the opening. These bushings are easier to make than a perfect long hole in the block. If there is play between the shaft and the two bushings, this tool will never run properly. Take your time to make these parts as correct as possible.
The block I made from a piece of 70 mm round mild steel. After the opening is cut the sides are milled away so that a square block occurs. It is easier to start with a round piece of steel than with a square piece of steel because a round shaft can be clamped easily in the three claw chuck on the lathe.
The bearing bushes have to fit with a slight interference fit in the block. If the bushings end up sitting a little loose, you can use a little Loctite to fix this. When this is done, the holes for the stop pins and mounting bracket can be drilled and tapped. The holes for the pins must be drilled with a drill of 5mm, 2mm deep so that the collar of the stop pins fit nicely against the block.
The hole for the 4mm steel locking pin must be precisely drilled so the pin fits perfectly in the hole. I drilled this hole with a 3.7mm drill and then drilled it out with a 4mm drill. For the pin I used the rear part of a worn 4mm drill bit.