Hi Ian,

Since I wrote that I have had occasion to make a PCB with very fine gaps and tracks. In this case it was a 10 pin DNF switch mode regulator IC with pads on 0.4mm pitch - the little Proxxon acquited itself admirably, although I did fit long springs to bias the X and Y axis and reduce backlash.

One point to note with the spade bits is that the 60 degree angle means that the cut width is very depth sensitive, you should ensure that the bed that you mount the PCB on is as true as you can get it or the variation in the cut width may make the job impossible. Outside of that, I think a LPFP100 should not be a problem.

As far as bit life goes, I could no more than hazard a guess that it is about twice the life of the common 30 degree engraving bits (sucks end of thumb possibly 10 meters with 0.2mm width)

Mike