Homebrew_PCBs

At 04:06 27/05/2002 +0000, you 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

I suspect this is to some extent inherent in the design of the collet. The
parallel shank at the rear of the collet is intended to help align the axis
of the collet with the spindle; however, if there is any play between this
& the socket in the spindle, then centering will be very hit & miss.

I would be tempted to try machining a tool holder that threads onto the
nose of the Dremel, drilled/reamed axially (while attached to the Dremel)
to the drill shank diam, & hold the drill with a small set screw against a
flat ground on the drill shank.

Regards,
Tony