--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> If you etch a small hole in the copper pad the drill will catch
easily.
> Now, in a drillstand, with carbide drills, the drill will not self-
center
> and it is a tedious process to lign up every hole. My boards are
actually
> worse since i have carbide drills and i do not like it, at all.
>
> ST
Why won't the carbide drills self-center? You are still etching the
guide hole? Are the carbide drills just so stiff that they don't
follow it? Could you reduce the pressure you use to hold the board
and let the bit "shake" the PCB into alignment? I have used carbide
drills in the past (it's been a while) and I don't remember having
this problem...
On the issue of guiding the drill in from below, can you raise the
press up so that the bottom of the table is at eye level and then
use a small magnifying mirror at a 45' angle just under the hole in
the table where the drill will come through?
Combined with a very bright spot light from above, there should be
enough light coming through the PCB to allow you to see the traces.
A small plastic pointer could be attached to the top of the table,
pointing to the place where the drill will come through. It would be
cut as a sharpened triangle from some thin plastic material like the
flat side of a milk jug.
If the pointer is adjusted to be just shy of touching the drill when
it is down through the hole in the table, then when the drill is
raised, and the PCB slid into place, the pointer will be visable
against the backlit PCB by looking through the hole in the table
from below.
In this way, the mirror or other optics do not have to be aligned
and moving your head will not move the pointer image against the PCB
since the pointer is rubbing on the PCB.
A convex mirror (like girls use to put on make-up) will give you the
magnification you want.