I thought some folks might be interested in how one of these are made, so here goes.
I start with a lump of 3″ OD C360 brass and carefully take a slice making sure its perfectly level on both sides. This is so the CNC has an even surface to carve on. The same is done for the Bronze coin cradle.
Next I spend an hour wet sanding both sides then buffing with three different wheels. I takes a bit of patience to get the surface to a mirror finish. From this point on it must be handled with the upmost care as it scratches easily.
The next part is all CAD and CAM. I find a good SVG of the coin logo and bring it into illustrator. Create a 2D layout with any detail I want to add to the coin.
Then it’s time to build a 3D model from this and create all the CNC tool paths, Bits to use, feeds & speeds etc. This can take an entire day and require constant tweaking after test cuts are made. Once it’s dialed in though, it’s good to go.
From this I generate GRBL files which are coordinates and other instructions the GRBL interpreter on an Arduino Mega will read. The Arduino will read and relay this information to a set of stepper motor control boxes. This is called a CNC machine. This particular one I built from scratch, just like these coins.
The Arduino and Raspberry PI and a mess of wires that control lights, speeds, proximity data and movement etc.
All stuffed inside an old toolbox.
The X,Y,Z work plate and gantry with spindle.
The prepped material is then affixed firmly to the work plate and the cutting begins. It can take many hours to complete with tool changes and tool path changes. If a mistake happens, I start again from the beginning.
After it’s finished, wood is selected, cut shaped, sanded and I use a Danish oil on it to seal and protect it. I use Cherry, Black Walnut, African mahogany and Philippine Mahogany.
A couple more hours of drilling tapping, painting and clear coating and tinkering and it’s ready to go.