Homebrew PCBs

--- In Homebrew_PCBs@y..., "alenz2002" <alenz@b...> wrote:
> 
> --- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:
> <snip>  The Dremel I once had was so out of round 
> > you could see the drill tip blur when it was running. Everything
is 
> made 
> > to a price.
> > 
> > Adam
> 
> Adam, I checked the runout on my Dremel a while back, and my first
> reaction was, 'Dang, I have a bent drill!' Turns out of course,
> the drill was OK but the collet is a piece of crap. I don't 
> remember the actual values, but everything except the collet was
> very near dead-on (by my standards). I have a bunch of Dremel odds
> and ends and none of the collets ran anywhere close to true. 
> The drill would be centered at the collet exit, but would, as
> you described, rotate in a circle at the tip. I intended to make
> a new collet, but never found the time. But by keeping the tool
> extended length to a minimum, I can live with the best collet of
> the lot.
> Anybody else checked this? Do I just have a bad (abused?) bunch
> of collets? An old one with a black oxide finish was better then
> the newer 'white' ones.
> Al

As Tony Jeffree pointed out the Dremel collet is a cheap 'n nasty
design. From memory it used a aluminium ('white') collet that was so
badly designed that it didn't sit neatly in its holder. The thing
could move about when the clamp was not screwed on. A proper collet is
constructed from grounded hardened steel ('black') so the collet fits
neatly in the collet holder by a chamfer arrangement. See some
pictures at http://www.indiamart.com/pgengineers/#products
I got my money back and instead bought an electric straight die
grinder for about 2.5 times the price. It was the cheapest solution
for reasonable performance. A little while later I noticed that a
commercial PCB shop near my area used exactly the same model die
grinders for their CNC drilling machine, and manual drill presses. For
anyone interested its this one 
http://www.bosch.com.au/productcatalogue/spt3/products/ggs27.htm

Adam