I don't make bracelets/bangles, but I was trying think of something with the 2 1/2 inch diameter you wanted and still be sturdy/bakeable. What about a 2 1/2 inch round cookie/clay cutter? The one I have seems very sturdy. The bangle should slide right off. If not, put some foil on the cutter, then slide it off. Hope that helps. If you could find the right size small cutters, might work for the rings too.