I have built my own. I am using Dremel and I could able to use 0.0135" (~0.34mm) bits without any breaking. I have also tried to use 0.0083" (~0.21mm) bits but no way with Dremel, I think 0.0135" is the limit. Cheers, Volkan
> ... is the Dremel run-out good enough for 20 mil