I started making rings with a lathe I made from an old small drill press that I had replaced with a nice Shop Fox a few years ago. I made mandrels for ID and OD so I could cut inside and outside of the ring. That was very tedious as I had to rely upon a tapered mandrel for the various inside dimensions. I tried to find a chuck that would fit the threads (european) to no avail. So I bought a Rikon mini lathe, and small 3 jaw chuck and a 1/2” chuck for the mandrel.
The first rings i did on the home made lathe turned out very nice. The left one is honey locust, the middle is osage orange and the right is walnut. I harvest the wood for all my work.
I can’t seem to get photobucket to sign me on in the service below.
Now I have bought a new Rikon mini lathe but it doesn’t seem mini to me. I also bought a small 3 jaw chuck and a 1/2 inch chuck to use with the lathe. The jaws on the 3 jaw chuck are just too shallow for my taste and also too big to fit into a 1/2” hole I need to use to make size 5 rings. When working on a ring I am either too close to the jaws either on the outside or on the inside if I am drilling. so I have ground the jaws so that they have more room to fit inside the ID of the ring. Unfortunately all I had was a hand grinder which I used by putting the jaws in a vise and grinding away the flat side of the jaw then put back on the lathe and grind the OD of the jaws while it was running. I worked perfectly. It’s something of a problem because the blade on a 4” grinder has a round profile which made it hard to grind the OD flat. But I got it.
Here is the 3 jaw chuck after I ground it to a size I could use. 
I’ve been trying (unsuccessfully so far) to glue plugs through the ring so that they will look like ovals when the rings is sanded with a rounded shape. I was successful with 2: 1/4” holly plugs but after I finished them they were so big they didn’t have the right shape when the ring was finished. So then I tried toothpicks. I have a large index of bits that are only a few thou difference at the tooth pick size but I’m having trouble getting them sized correctly. I’m going to try the over sized bit and see if the super glue finish might fill up some of the gap. The next size down was only 1 thou difference but the toothpicks broke before getting fully inserted. Not good. Sanding a toothpick to size by sanding off a half a thousandth is not my idea of fun. But I may have to try it. Maybe 1000 grit would work but uniformity will be the difficulty.
Now I’m going to try something a little easier, I hope, by making a 1/4” stack of walnut and maple veneer and using it to make a setting in the ring. I’ll cut a dado and glue in the stack before I drill the hole.