Basic segmented ring construction
This page shows how to build a basic segmented ring. Most of the time I use a miter saw to cut the segments because it's much faster than a tablesaw. For dimensions a segmenting software program is suggested or you will have to draw out the ring on paper and measure.
To begin rip a board to the required width and if the thickness has to be reduced now is a good time to do it. The better the stock is prepared the better the ring. This means straight, square with parallel edges. The picture below shows the first cut. In this case the miter angle is 15 degrees because I'm making a 12 segment ring.
Next flip the board and mark the segment length as shown in the picture below. The segment length is always measured from the long point. Now bring the blade down to the board (saw off) and line up the cut. Next put a pencil line on the fence. You can see the line on the fence at the long point of the board in the picture below. This way you won't have to measure every segment. Start the saw and cut the first segment. Next flip the board over and put the long point on the line you made on the fence and cut the second segment. Continue this process flipping the board each time until you have all the segments needed for the ring.
Next you need to true each segment. I true each segment by hand using a sanding disc glued to a piece of countertop. With even pressure just drag the piece across the disc a few times and it will be trued.Next we will glue the segments together in two half circles. Lay out the segments in a half circle (no glue). Check that all the joints are ok. If you have some bad ones try flipping them over. Sometimes if there is a slight alignment error in the saw this is all you need to do. It's a good idea to keep your saw in alignment by following the manufacturers directions.Now glue a half circle together. Using a flat surface like a piece of countertop is essential or you won't get good joints. When gluing rub the segments together to get rid of excess glue. (Be sure not to use too much glue). When you begin to feel resistance in the joint line up the edges and stop. Do this until you have formed a half circle. Leave it to dry. There is no need for clamps. If your segs were trued and the joints were good the ring will be just fine without any clamping. The reason for building rings in half circles is so we can correct them. Thats why we build rings that have an equal amount of segments per half ring. For example if you build a ring with 5 segments total you will not have two half circles. I true half rings on a disc sander but if you don't have one you can use the countertop/sanding disc method. Stand up the half ring on the disc and start correcting. It takes a few minutes this way but it will do a fine job. Before I had a disc sander I corrected all my rings with this method.
Glue the two halves together and your almost finished. Every ring needs to be flatened. I do this with a performax but if you don't have one its back to the countertop method. If you are doing it by hand you normally only need to do one side. You can correct the second side on the lathe when you glue on the ring. If your building the whole turning off the lathe you will have to flatten both sides.