I’ve been busy with my CNC milling machine, and anything flat (minute recorder springs, setting lever springs, etc.) is no problem at all.

The final frontier are of course wheels and pinions. The fourth axis motor that came with the milling machine wasn’t very accurate, so I had to modify it in order to be usable for watch parts.

A good indicator how small you can machine is making a small pinion. The one in the photo measures 2.5mm across, and has 18 teeth, so that’s not bad for a start.

The main problem was getting a perfectly round base for the pinion, and I achieved that by milling down the round stock in the fourth axis itself, so basically using it as a lathe. The pinion end and the shaft that you can see where milled down (that’s why they aren’t that smooth), and they would get finished off in the lathe if this was a real-world part. At the moment, I’m testing the limits of my CNC milling machine, so it’s good to show what finishes you get straight out of the machine.

To see how the set-up works, here is a video of the mill in action cutting the pinion you have seen above:

The same thing but seen through an electronic microscope (the video is taken from the microscope screen) shows a lot better what is happening:

The GCode for the wheel cutting was generated by my own little script, which you can use yourself at http://watchguy.co.uk/cgi-bin/cnc?action=wheels free of charge.

To make it look nicer, I finish off the pinion in the lathe.

If you know your watch parts, you might notice that the tooth shape isn’t quite right. I’ve cut the teeth with a Kyocera thread mill, so it’s a 60 degree triangle that’s cut into the wheel. The next step up will be to find wheel cutters small enough (module 0.08 – 0.05) to make proper wheels …