Homebrew PCBs

"AncelB mosaicmerc@... [Homebrew_PCBs]"
> I use resharpened carbide in my dremel 395 with 1/8" shanks for PCB 
> work.  They work fine....I go down to around 0.31 mm. I can go smaller 
> but bit breaking happens every 10 holes or so.

Me too, but I rarely break bits since I switched to a home-brew drill
stand that seems to eliminate any "hand wobble" from causing breakage.

My CNC machine can drill lots of holes with resharpened carbide and a
Grizzly pencil-style die grinder.

Perhaps rigidity in the holding of the dremel is more important than
runout?  Or at least, *lack* of rigidity is more common as a cause of
breakage?