Coin Stamping

• Permanent metal molds: design and material choice

• D2 tool steel: microstucture, machining, heat treating

• Coin minting: material ductility, required press force, design considerations

• Machining copper and aluminum in annealed vs work hardened states

• Using small end mills: roughing with 1/32 ball and then finishing with 10thou ball engraving bit

For the industrial materials project in my material science course, James, Jacob and I decided to make a permanent metal mold with the goal of casting coins and analyzing the D2 tool steel that we chose to use in a number of different ways. This project was a failure in the traditional sense, we were unable to cast coins as the sprue was too small and the back pressure forcing the metal into the mold far too low. However, we were able to make some wax coins for lost wax casting, as well as using the mold and a 50ton hydraulic press to mint some coins which was a great pivot. Ultimately, the two part mold wasn't well designed for pressing as there wasn't a great way to remove the coin after use but we did still learn a ton and made a couple passable metal coins. Full credit is due to James who did all of the 3d modeling to make the CAD for the mold as well as Jacob who made the video. I worked on the machining of the blanks as well as the analysis of the D2 though the heat treatment process. I found it super interesting learning more about tools steels in general, and feel like there is so much more that I would like to investigate but it also seems that when it comes to real world use, there are a lot of confounding variables that also impact the steels performance. Check out the video above that Jacob made to learn more about the project.