Making a ball bearing on the lathe
The outer bearing race needs to have a round hole in the middle. I couldn't cut that with the bandsaw, and didn't want to cut the 18 mm Baltic birch plywood on the scroll saw, so I used a drill press circle cutter.
I cut from both sides. Before finishing the cut on the second side, I clamped the workpiece to the drill press table because, once the circle cutter breaks through, the stock has a tendency to jump around if it's not clamped down.
The outer ring is made of two layers of Baltic birch. I cut them out before gluing them because the circle cutter isn't very good at cutting deep holes. First I clamped them with weights, but once the glue partly set, I switched to clamps. If I clamped it right away, the glue (being a lubricant) would cause the joint to slide out of alignment.
I also added a 8 mm thick sacrificial layer on the bottom. This layer has a hole in the middle, which allowed me to line it up with the faceplate of my homemade lathe. I first clamped the workpiece to the faceplate...
It would have been tempting to use a parting tool to cut it off the sacrificial piece, but I would have hit the screws I used to attach it (this might have worked if the sacrificial piece was much thicker)
I then put the piece on my small table saw sled, with a block on the right to ensure I put it in proper alignment, and cut the sacrificial piece off one part at a time. Doing this sort of operation without a sled would be very dangerous. With a table saw sled, it's only a little bit dangerous.
Then cleaning up the cut on my homemade belt sander. I use the sander for quick operations between other steps quite often, so having the sander with it's own dust collector helps a lot - not having to worry about opening blast gates or turning on a separate dust collector.
Then, with the marbles spread around the circumference, the hub is locked in place. But there needs to be something that keeps the balls evenly spread around so they don't bunch up on one side.
I fully cut the inside holes of these rings with the circle cutter as well as most of the outside, but finished the outside cut on the bandsaw. It would have been too risky to fully cut the outside of the rings with the circle cutter as well. The ring would probably have gotten loose and smashed by the circle cutter.
I then needed to drill some holes just larger than the marbles But with a drill this large in a workpiece this thin, I was pretty sure the drill would tear it up unless it was very well secured and clamped together.
So I made a jig to fully support the ring on the bottom and squeeze it from both sides while drilling.
My initial intent was to screw the two halves of the ring together, but even #4 wood screws would have been too big. So I drilled some holes through both pieces and snaked some copper wire back and forth to hold them together.
With the main purpose of the bearing being to look cool, I opted for a different solution.
This way, I could fill the entire bearing with marbles.