I have always had trouble with front to back alignment of the drill bit. I came across this idea on another forum. I lost the link, but did copy the text. This was in response to the camera and bottom drilling idea posted there.
Begin Quote...
"A better way...
..is this
1) Mount a large-ish box on the drill press to act as a platform,
say a cigar box.
2) Using your pcb drill (0.8mm) in the drill press, drill a hole
in the box you just mounted on the drill press.
3) Now mount the laser pointer in the box, pointed vertically
up through the hole you just made.
4) The red spot is the exact diameter of the drill and is
(just) visible in the hole in the gap in the centre of the
pad when the PCB is at the right spot
works for me using FRG4 glass fibre PCBs.
End quote...
This is a clever idea and it works, but my implementation is a bit more sophisticated than the cigar box. I use small project case, a laser module mounted horizontally, a 45 deg mirror and brass shim stock to form the PCB illuminating beam. The mirror re-directs the beam 90 deg upward to a pinhole in the shim stock which acts as a spatial filter to form a nice tight beam. The shim stock is held to the interior of the box under a larger hole in the lid with double sided tape. Once everything is positioned, fasten the lid and drill the finest hole you can through the shim stock. I find that this very precisely locates the tip of the drill bit; it's right where the center of the dot is on the PCB. There is, however, some spreading of the beam as it passes through the FR4. Also, if you move the drill head sideways, you will need to replace to the shim and drill another hole.
I find that it is easier center a dot on the PCB than it is to try to position the tip of a tiny bit. I also wear 3.5 reading glasses.
Baxter
--- In Homebrew_PCBs@yahoogroups.com, "Frank P" <qz9090@...> wrote:
>
> Carl,
> Another easy and cheap solution is to mount a laser pointer showing where the bit will hit the PCB.
>