I forgot to mention there is a polishing tape called "crocus cloth", probably a brand name, used in factories. It is on a cotton base, made of carburundum, or diamond chips. It is flexible and about 1" wide, which is good to polish steel parts. They use it to polish crankshafts on autos and tractors too. I have lost my source, but am looking on the internet for a new source. Don't care what it costs. It is worth it. Maybe try a machine shop.