Homebrew PCBs

We have a PCB layout guy here at work that worked most of his life at a PCB
house before working for us. He says that all those 'reconditioned' bits are
because the PCB industry needs such incredibly tight tolerances in hole
width, that after a certain number of holes, the drills are out of 'spec'
and can't be used. They aren't that dull, they're just a bit too narrow for
precision use. They stop using bits if they are actually out of spec or not
- there's just a certain limit (number of holes I guess) and after that
limit, the bits are discarded. They can be cheaply re-sharpened and sold to
people like us, so throwing them out isn't all that expensive for the PCB
house as they get some money back for their investment. My friend said that
it's much more expensive (because of an increase in the amount of 'errors'
in a board) to use a bit that might be out of spec than to just use new bits
every x holes. I couldn't believe the tolerances he was talking about in the
higher end PCB shops. These guys really have their processes down.

*Brian

> Dave:  GOOD questions, and ones I think worthy of discussion 
> "here"!  I have 
> wondered this myself, and I have had to rely only on my 
> "imagination" for 
> answers, as it is not SO earth-shaking a quest that'd I'd 
> "get in the car and 
> drive about to the several PC-houses within 50 miles, to inquire"!