Hi Richard,

I use drill bits as small as 0.5 mm (19.7 mil) and as large as 1.0 mm (39.4 mil). I have only had one break in all the time I've used this machine, and that one only broke because I was putzing around with the head while it was running and inadvertantly stopped it from raising fully before it began to move laterally. As a drill this machine works beautifully.

As for it smearing the copper instead of milling it (not part of the drilling cycle by the way), it sounds to me like he's pushing the tools past their lifetime. The smaller the tool, the faster it needs to spin and the shorter it's lifetime will be. None of these tools last forever, but the really small ones die quickly. That's why I said I wouldn't pay for the tools necessary to achieve 4 mil lines and spaces. Even with the 8 mill universal cutter that I use, the suggested lifetime would be about just enough to do one of the boards I showed in my last post. That's why I too use my tools past their suggested lifetime, but I do so understanding that I have to watch for degraded or incomplete milling. If I were trying to do 4 mil lines and spaces, that same board would have needed at least two bits, even after pushing them past their suggested lifetime.

How your friend is managing to break a bit a minute is beyond me. I would have to be really very careless to break a bit a year, and monumentally careless to get that up to a bit a month. I really couldn't even guess what your friend must be doing, but I can confidently say he should stop.

Later,

Joe