Homebrew PCBs

On Thu, 13 Jan 2005 01:46:58 -0000, James Newton  
<jamesmichaelnewton@...> wrote:

>
> 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...

They cut so well they will also cut into the side of the pad. i will try  
making the drill table more slippery.


> 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.


Interesting idea, but i will still try projection first, today i hope.

ST