Routing Bullnose on Inside of a Circle
I'm trying to make a set of wooden gymnastics rings. The inner diameter is 8". The thickness of the stock is 1 1/4".
I have a 5/8 bearing guided roundover bit; however, I find that my reference edge is removed by the first pass, so that when I flip the piece over to rout the opposite edge, the second pass cuts too deeply. If I lower the bit (so as to keep the reference edge intact), then I don't get a true circle profile, but rather a flat spot along the centerline.
I also have a 1 1/4" bullnose bit that will cut the entire round profile in a single pass. This eliminates the flat spot or vanishing reference edge problems, above. The bullnose bit does not have a bearing to guide it, so I use the router table fence the rout the outside edge. Any suggestions as to how to rout the inside of the circle using the bullnose bit? I was thinking a round fence that matches the inside diameter of the circle with bullnose bit positioned through a hole in the circular fence so that the cutting edge protrudes a hair past the edge of the circular fence. Any suggestions would be most welcome. Thanks!