In trying to mill an autolevelled board at a low feed rate,

In trying to mill an autolevelled board at a low feed rate, to a depth of 0.05mm I have now broken eight supposedly strong (carbide) drill bits. All are fluted rather than V shaped.

The board is fr2 so soft.

No spindle speed control so going at full tilt of 12k.

Whilst I think the autolevel is not working properly due to inadequately straight leadscrews it is clear that I’m probably using bad quality bits (although they were 4£ each).

Is anyone aware of good quality end mills in Europe? I’m looking for 0.2 and 0.3mm primarily (many fine pitch ICs)


I accidentally used drill bits before and learned the hard lesson that some ebay sellers list drill bits as end mills. The drill bits would crack instantly.

these are the ones i have been using:

Hmm. They do look like end mills. I’ve only broken 0.3mm ones when trying to auto-level and couldn’t get enough voltage through the tiny tips so gave up. I do run my jobs pretty high up for a first pass so I never get high spots on the FR4 that are so deep I’d break the tiny end mills. I’ve mostly used Kyocera Tools end mills.

thanks John. I have not seen a method in the eagle board widget to specify what the maximum pass depth is for trace milling. That would be useful.

Oh, I just cheat and set my Z zero like 0.1mm too high from the true Z zero. Then run the job. Then go down on Z 0.1mm to get back to true zero and then run 2nd time.