I needed some small rings which I could weld onto various things I wanted to hang on pegboard hooks so I got out a vise tool I had made for this purpose. It was made to roll rings from 3/16” round rod with a inside diameter of 1/2” using torch heat.
I wanted the new rings to have a somewhat larger inside diameter. so I cut a short length of the right size pipe to use as the mandrel and just tacked it onto the shaft of the original tool. I then tacked the end of a 3/16” rod to the added pipe section and did the wrapping. After rolling several rings I cut the coil end-to-end releasing the individual rings and cut the tack to remove the last one.
This one tool can make rings of several diameters by changing the size of the pipe mandrels.