PCB success!

[R.G. Keen]

>>I'm putting together the illustrations and pictures for an article with
>>detailed instructions and diagrams on how to convert a Dremel press 
>>into a PCB drill microscope. My proto makes drilling easy and simple.
>>A 300 hole board is about 10 minutes.

>This is really overkill. If you have etched pits where the holes should be, the 
>drill bit will steer to the correct position automatically, as long as you get 
>the tip of the bit somewhere in the pit. This can be done without a microscope 
>and just as fast. 
Yeah, I did it that way for years - twenty five of them, about. There is a
distinct self steering to the pit in the copper. It's OK, and very usable. 
However...

>Just make sure that you use a normal bit and not one with 
>reinforced shaft. Using Pertinax boards instead of glass fibre means the drill 
>bit doesn't get blunt. They are cheaper and  look more retro too. 
... if you use steel bits, the points dull after about a hundred holes in glass
epoxy. If you use carbide, the points last almost forever as long as you don't 
break them, and it's like pressing a needle into butter to go through the boards.
Using Pertinax (which I don't know, but I assume is a much softer material) would 
probably give longer bit life for steel bits. The softer materials are not
generally available here in the USA, what is common is FR4 glass epoxy.

>If you don't have etched pits in the board, the drill will wander off and flex, 
>no matter how exact you position the spindle. So in that case a microscope is 
>largely wasted.
With carbide, there is very little wander, as the bit stays sharp enough to cut
wherever it contacts; you have to be VERY gentle to get any self guiding with 
carbide. The bit is so stiff that there is little flex (but they WILL break!). 
The bit may push the board to one side a bit if you're on the edge of a copper 
land. Very often, the bit cuts a dimple wherever it contacts, so off-center 
holes in pads are a problem - at least for me.

However, no wandering is one of the advantages of the drill microscope. You drill 
up from the bottom, which is not differentially printed with copper. There is no 
wandering as the surface is flat and uniform. You get a hole wherever you are
looking, guide dimple or not, and I suspect with steel bits as well.

I used to use a very sharp pointed awl and prick punch dimples in the center of
pads as guides for drilling, and that was even better than the etched guide 
center, by the way. You might want to try that.

>I don't doubt that a microscope could be helpful if your eyesight is reduced, 
>but don't make the assumption that it is necessary for drilling boards.
I don't assume it. In my opinion, the drill microscope is a real advantage in 
getting greater ease and accuracy. It can certainly be done other ways.

Can you drill PCB's without a drill microscope? Sure. I did PCB drilling freehand 
and with a small drill press for literally decades. 

Is it easier and more accurate with a drill microscope? I think yes. That is
just my personal opinion. Anyone who doesn't think so doesn't have to go to the 
trouble and expense of making a drill aid. It's just another tool. There are other
ways.

Is a drill microscope more expensive than just a drill, or just a drill press? 
Sure. However, if you have a Dremel Moto tool and the drill press accessory, 
the drill microscope add-on is probably only going to cost $30 to build. I'm not 
familiar with the Unimat, but I suspect that something similar could be done.

Is it worth the effort and money? 
Depends on each individual's situation and needs. I drill a LOT of holes. For me 
it is. Maybe for others as well, maybe not.