Hello Stefan...and all. My first thought to your question, like one
other member...was to suggest using a LASER Pointer to "project" the
contact point of your Drill.
Simply put...Drill a hole and without moving the PCB align the Laser
pointer to AIM at the Hole. Then do a few test drills to confirm your
alingment.
I have a pointer I grabbed at a local Dollar Store that came with 5
different heads. None (other than the basic Dot pattern) would be
useable, but I've seen pointers sold on E-Bay that come with 42
different heads !!! Who knows...maybe one will be an
appropriate "PATTERN"...like a Bull-eye for example.
All due respect but incandecent light bulb, brass tube, "Wires" as
crosshairs and such seems like a lot of EXTRA effort to save a couple
of dollars (Pounds, Euro,Francs,etc) on what a pointer will cost. In
either case you'll have to jury rig an adjustable mounting method to
hold the "light" source.
Lenses, light sources, screen, dust collectors etc seem like again a
lot of work unless you've spent weeks (months) on building a fancy
CNC machine (in which "going all the way" would be justified).
My two cents worth....take it with a grain of salt (Unless high blood
pressure keeps you on a salt reduced diet...in which case...don't
mind me! ;)
Cheers...Dean.
--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
> Hi everyone,
>
> remember some time back we talked about PCB drill viewing
mechanisms.
>
> I want to make one for a pivoting drill stand, with the drill from
the top.
>
> I think, please correct me, it could work by illuminating the PCB
with
> bright light from below, then taking that reflected light and
sending it
> through a convex lens which sends it to the projection screen. a
mirror
> will be required too.
>
> i'm not too good with optics, but i took a lens, illuinated a piece
of
> newspaper and tried to project the image, which worked to the
extent you
> can expect from a flashlight.
>
> Now i wonder where to put the screen, it could be under the atual
drill
> table, on the front of the machine.
> Not ergonomically ideal but if the machine is positioned relatively
high
> it might be acceptable (the screen could be angled to get a better
view).
>
> Another option would be to have a slightly tilted-down screen on
the top,
> back of the srilling machine.
> the image would be projected diagonally up through the work surface
of the
> machine (cutout).
>
> Each setup requires a lens and a mirror, but the screen-on-top
version has
> a much longer optical path.
>
> How can i work out which lens size and focal length i need?
>
> ST