I'm trying to figure out how to make a broaching die that will cut the spiral pattern seen in this picture. It is the tip of a ram rod made in Germany about 1750. I have a lathe and a mill/drill to work with. I suspect it was made with some kind of spiral cutting tool such as the long bench rifling tool that put rifling in barrells. This thing is only about 3" long. Other than laying them out and cutting them by hand any ideas?