I first tried using a scroll saw and a diamond wheel to cut the metal. You'd think I was trying to cut it with a butter knife. I ended up drilling several holes and breaking it free in a vice.
Step 2: Set it up for the lathe
First drill a pilot hole. Then proceed to a 1/4" bit. Now you can mount it in a nut and bolt making it ready for the lathe.
Step 3: Machine it down
Really you're making a titanium washer. I never did any measuring. I just machined it down until I thought it looked good. It's about 3/4" in diameter.
Step 4: Size your ring
As you hammer the ring against a mandrel (I'm using a pry bar) it will expand the wall of the ring. A few things to keep in mind. While you're hammering the ring will have sharp edges. As you're trying on the ring these edges will catch on your finger; making you think the ring is smaller than it really is. Remember you can always keep hammering but you cannot shrink the ring. Make sure to check that you're not over hammering any single section of the ring. It should have an even thickness all the way around.
Step 5: Comfort fit
Once the ring is the proper size I put it in my lathe. Use extreme caution if you're going to do like you see here. A flying tool bouncing off 1100 RPMs can land you in the emergency room. This it where I rounded over the edges on both the inside and out. To make sure the ring stayed square I used several nickels to line it up in the jaws.