For our skill builder on the CNC machine, I wanted to see if I could design my own joint. I went with the idea of routing concentric circles to create a joint that could rotate. I divided a circle into four segments, the inner circle, and three concentric rings around it. For one side of the joint, I would create a pocket cut of the inner circle and the second ring, and the other side side of the joint would have a pocket cut for the first and third ring.
Here are the four circles all together, these were then glued together to create a stackable arrangement.
Here is a single piece after the glue up, and then the two pieces side by side showing the mirrored sides.
And here are the two pieces fit into each other.