It was done partly with a mill, refined with a file and sweet talked with a little profanity. As far as the type of steel I am not sure, the machinist said it could be case hardened when I get to that point.
As I got closer to the final slope I would cut a test board, to kind of train myself not to be rough on the jig I would mark the cutting edges with a magic marker. After a few of the test boards I could do the cutting without scraping the marker, with practice I would estimate that this jig could last quite a few years without hardening. I am cutting the boards a little big so that I can sand and polish a real smooth top to the board.
BigB, I made the back end short so that I could use it to make my one piece open reeds with a bell and not have a long straight 5/8" rod as part of it,. I am thinking about cutting off another about 3/8" off of the end, but need to make an open reed one piece first to see what it will look like with out the cutting.
I started today on a Louisiana style duck call jig. I will post a picture whenever I get it done. This is a lot more complicated than the simple slope of this one. It will also take quite a bit more file work and sweet talking to get it finished.
Marvin