Hi Ralph, I used a sprocket with another sprocket welded to it. Something I tried that didn't work clamped in the vise. Usually I go to Home Depot and get a 2x4' piece of MDF. If it's 3/4" and I need a 1" thick piece I glue and nail on a 1/4" piece of plywood if they don't have MDF that thin. Mark out the shape you need, cut it out and drill a hole in the MDF where one end of the tubing will be and use it as an anchor point and put a small muffler clamp or U bolt through the hole and tighten it down to hold the pipe against the MDF. Longer the tubing is the better so you can increase the leverage. I have a 12" disk sander but belt sanders or an angle grinder work to smooth the working surface of the form if needed. Small pieces of wood nailed to the sides of the form as I mentioned keep it from sliding off. Hope this helps. Steve.