Seems like changing out a broken bit would be a PITA if it's located
under a stage or table. For manual drilling, I just don't see the big
advantage of the "bottom up" method over a standard precision drill
press with an illuminated magnifier attached. Another advantage of a
regular drill press is that it can be used for other types of drilling,
not just PCBs.

Leon Heller wrote:

"Tim Killian" wrote in message
...


wrote:


A fair bit back, Jim Rozen described a drill press for Printed Circuit
Boards that sounded like a good design. A microscope with a cross hair
to align the board, and a drill that comes up from the other side to
drill the hole.


Dust? Drilling PCBs makes lots of abrasive dust that will get into your
bottom motor spindle bearings. If the board is already etched, you don't
need a microscope or cross hairs to align the drill bit in the center of
the pads. The lack of copper in the middle of the pad will center the bit
automatically if the operator can get it reasonably close. And if you need
better accuracy than that, then CNC is the way to go (it doesn't need the
microscope or cross hairs either).


The old Excellon PCB drilling machines used a similar arrangement. They had
a projection microscope that displayed the pads on a ground glass screen,
with cross hairs. I'd be inclined to use a web cam for viewing the pad.

Leon