More PCB Milling

I'm experimenting with milling more detailed and double sided PCBs. So far I have tried a smaller cutter (D bit) that was 0.1mm, but I suspect turned out to be a bit larger than that. The fine tracks have disappeared in a few places so it's not usable, but overall it's encouraging.

The four large holes are my attempt at registration pin holes, which failed as the PCB software auto centres the artwork so when I milled the traces they weren't registered with the pin holes properly. I need to experiment with methods of creating these holes.

The second attempt at the double sided OLED watch PCB was more successful. I mistakenly drilled the via holes from the wrong side, I hadn't remembered that the holes are drilled from the bottom of the board, so I milled the top side tracks then drilled holes. Of course they were wrong and this PCB has an extra set of via holes. It is probably just about usable, but I am going to make a new board more suited to milling and also add some of the circuit changes as well.

This second PCB looks a lot better. I cleaned the copper up using some fine wet and dry paper as there's a lot of rough burrs as it comes off the milling machine.
The blue PCB is the one I had made in China, for comparison.

The registration using pins worked well, the program I wrote to generate the pin holes now uses the board outline, which has to be the correct size.