Hey everyone, first time post. I am using a similar design to a RS-CNC32 (https://www.makerfr.com/en/cnc/rs-cnc32/) to mill PCBs on FR4 copper clad board. I flattened out a piece of waste board, mounted my blank to it with some custom clamps and tried a variety of bits. At first I tried a 60deg bit but the height variation was horrible. Then I bought some 20deg ones and the height variation was still pretty bad, and causing traces to be too thin/thick. I think the 20deg bit was slowly chipping away as it milled because when it finished the end was almost flat.

I decided that I would go for the smallest flat endmill I could for QFP pins (0.55mm) and bough a pack of 5 from drillman1 on ebay. As soon as the bit hit the copper spinning at 25000rpm it snapped. And then another one snapped as I was zeroing the height. They are so delicate! How is it going to take any cutting forces if it can't even touch off on the material?

Anyone have any tips on what to do? I can provide any details necessary to help.

Thanks in advance,
Clayton