I want to turn copper tubing into medallions or custom coins.
It would be far easier to use copper sheet and strike the coins (as in ancient times). Copper doesn't cast well, so melting the tubing's not really going to work. So, forget the tubing and find a metalsmith--check your local colleges to see if they offer metals in their art department, and if they do, contact the professor, who will probably farm it out to the students. Failing that, get in touch with a jeweler. They can get copper sheet of an appropriate gauge and, following your designs, make your coins.
