Here's my first Instructables project and I made it at Techshop. A shiny new 58.4mm espresso tamper! I started with a 2.5"x12" copper round rod and a basic understanding of how to use a metal lathe and a vertical mill. As it turns out, making a round thing into a smaller round thing just isn't that difficult.
I used a steady rest because the material I was working with was too thick to fit through the headstock of the lathe and too long to be stable on its own. First I machined the face flat, then brought the diameter down close to the final dimension I was looking for - in this case I ended up at 59mm with the plan that the finished tamper would be 58.4mm.