Ball Bearing Milling

To start, I wanted to find a secure way of securing the bearing. I knew that because of the scale and because it was a sphere, most traditional options would not work. This took a bit of thinking. I actually started by sketching out a spare drawing of the final piece. Here I realized that the ball would only need to be operated in one position. Here I realized that if I could expose the top part of the bearing, I would be able to mill the top, and then drill the hole. Additionally, I would be able to achieve this by drilling a hole that only allowed for the part of the ball to be exposed. I could then drill and tap a larger hole to beagle to use a bolt to secure the ball from moving. 

After creating the fixture, I tested using a polyethylene ball bearing. I used a treaded rod with a jam nut to secure the ball from moving. In milling I saw that the ball was spinning with the drilling operation. I added a split washer to the top of the rod, this allowed for a line contact rather than a point contact. This worked well and was able to secure the ball. I then transferred to milling with stainless steel; however, I found the threaded rod was not able to apply adequate pressure to secure the stainless steel bearing and it was able to spin. I then switched to using a hex bolt, which allowed for me to further tighten the ball bearing. This worked well, in being able to get the required operations completed; however the washer left a ring imprinted on the bearing. In the quest for this to be more accurate, I found a serrated-cup tipped set screw that I thought might be able to help me get the wanted results.