Got this yesterday:
This is a socket bit that can be chucked in a drill and used to grind coffee with a manual burr grinder. I'm toying with the idea of having some CNCd, but this 3D printed steel version will work well for testing.
I don't own the Hario grinder that it's designed for, but I'm hoping to test it this weekend at a friend's house. Expect results soon :)