It sounds like a great idea, but I need some clarifications. You mount the camera horizontally, the optical path deflects straight up through the mirror and you look at the component side (bottom side, the board is upsidedown) of the board through the hole in the drill press table. You then mark the point of exit of the bit with black tape on the computer screen, correct? Then to clearly see on the camera the hole in the middle of the pad you need to shine light through the board (the copper side is on top because the entry hole is a lot cleaner than the exit hole). Now, the light cannot be collinear with the bit, because the drill head is in the way, so it shines at an angle, which produces the same parallax error you are talking about. What am I missing?
Thanks for sharing your clever setup,
Fabio
--- In Homebrew_PCBs@yahoogroups.com, Mike Bushroe <mbushroe@...> wrote:
>
> Another technique for getting more accurate hole drilling is to put a tiny
> mirror, mounted at a 45 degree angle underneath the table of the drill
> press. Then mount a small circuit board
> camera<http://www.supercircuits.com/Security-Cameras/Board-Cameras/PC302XS>for
> under $20 or better yet aUSB microscope
> camera<http://www.amazon.com/Celestron-44302-Handheld-Digital-Microscope/dp/B001UQ6E4E>for
> $50-60 so that the camera see the bottom side of the board you are
> about to drill. Drill a few test holes and mark with thin strips of black
> tape the exact point that the drill bit goes through and then you can drill
> the rest of the board(s) quickly, easily, and with great precision. It is
> well worth the time to tweak the mirror and camera so that the drill bit
> moves EXACTLY straight up and down, because it eliminates parallax errors
> when the board does not lie exactly flat on the table.
>
> This technique should work well on any drill press where the up and down
> motion is exactly lined up with the rotation of the drill bit. I think that
> the Harbor Freight elcheepo bench top drill press I did this on was off by a
> few degrees. It made it a little harder to guess where the drill bit would
> first hit the board, and confuse you by having the last image of the drill
> bit all the way through the board being offset down and right. But, if you
> are no long young and don't still have 20-15 eyesight with focus from zero
> to infinity, this makes precision drilling a whole lot easier.
>
> I wish I could take credit for this, but I stole the idea from the guy
> whole PCB Fab in a box.
>
> Mike
>
>
> [Non-text portions of this message have been removed]
>