When you glue together all the segments of a ring you'll quickly learn an awful secret. No matter what you did to true up your saw, the glued up ring will not come out perfectly flat. That means you will have to find a way to get at least one side trued up so you can glue it to the next ring. Here are some of the ways you might try.

Both the Surface Planer and the Drum/Thickness Sander require assistance to hold down small rings. Otherwise they'll just pick up the rear edge and make a mess. Just weakly attach two boards on opposing sides of the ring; use something like hot glue or double-sided tape. Start with boards that are about the same thickness as the ring and are a foot or so long. Process both sides and then remove the "sacrificed" boards. This would also be a way to safely use the Wagner Power Planer in a drill press.

The Drum/Thickness Sander deserves some extra explanation because of the quality of the result. While commercial units start out in the $800 range, you can build one yourself for about $100 if you have a spare motor lying around. The people at Moritz Designs have a plan for sale, at just $9.50, that is easy to follow. You’ll find it at http://www.moritzdesigns.com/sander/sander.html.

I have just one tip for improving on their design of the table that your work rests on. That is to put ¾” plywood on both the top and bottom sides of the table to maximize its stiffness. The extra stiffness will ensure that the clearance under the drum is constant for its entire length.