Homebrew PCBs

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