Drilling PCBs

[R.G.]

Any tinkerers in the house?   

Drilling comes up fairly often here. I thought I'd share a trick that was old before the internet existed - the drill microscope.

Drilling PCBs used to be done entirely by hand, much like we do in our amateur attempts. They'd spot the holes and then eagle-eye the location of every hole. The results were - well, variable. And what if you sneezed?

The biggest problem with this is that of course, you can't look straight down on the spot to be drilled - the drill is in the way. Some clever guy figured out that if you drilled from the bottom, you could see the location for the hole just fine. Only problem is that now you can't see where the drill is.   

Enter the drill microscope. This is an optical widget which looks right down onto the table the PCB sits on to be drilled and has an optical crosshairs to aim at the hole's location. Generally some optical "gain" is involved to get a better view. Looks something like a microscope over the PCB. The drill is put UNDER the table, and arranged so that pulling the lever or pushing the foot pedal, whatever, makes the drill rise straight up. The microscope part is adjusted until its crosshairs point right down the middle of the drill bit.

Now you move the PCB until the place you want the hole is right under the crosshairs, clamp the board in place and pull the lever/pedal that makes the drill rise from the bottom. As long as the board doesn't move, the hole is in exactly the right place, and you can see well enough to make sure that's true. Broken drill bits mangle things up, but hey, nothing is perfect. Don't break your drill bits. 

The microscope sounds like a big issue, but it's not. Go down to your local hunting supplies store and buy a cheapo 4x rifle scope with internal crosshairs. These are usually WELL under $20. These will not focus to as close as a couple of inches from the lens as is. But if you unscrew the eyepiece and extend the length from the main optics barrel to the eyepiece, they WILL focus down to a couple of inches, and you have a ready made crosshairs microscope. Rig some kind of sturdy arm over your Dremel drill press, which has been rearranged to drill UP, and put the table on top of the drill. This can be done with the stock Dremel table. Or it could back when I last bought a Dremel drill press, maybe 25 years ago. These things don't change much. The arm holding the microscope has to be sturdy enough so looking through it and bumping it as you use it does not misalign it.

That's it. Line up the drill bit and crosshairs and start drilling.

This is a home hacker's version of the big industrial stuff that did PCB drilling throughout the 60s and into the 70s. The big industrial drill microscopes were sturdy and repeatable enough that they would stack up maybe 5-10 boards  and drill them all at once.

Just thought you'd like to know.

[Gus]

R.G.

What if you used a front surface plastic or stainless steel mirror?

Drill a hole at the center at 45 degrees a little bigger then the drill bit

Use pinstrip tape or draw or a crosshair on the mirror
 
Make sturdy mount to hold the mirror at 45 degrees to the drill press table were the drill bit will cleanly pass thought the hole. This would mount to the post

Use led lighting to illuminate the PCB

Line up the PCB with the crosshairs and drill

OR use the 45 degree mirror without crosshairs and mount the scope to the mirror and post, then align the cross hairs to where the drill bit center is.

One could also modify a web cam or security cam or old video cam or ? to view things on a monitor

[davent]

R.G., I always liked the sound of your ideas in this one, i've got one of the old school Dremel presses i think i've worked the kinks out of so someday may get around to giving this a go.

http://www.diystompboxes.com/smfforum/index.php?topic=81837.msg678444#msg678444

[R.G.]

What if you used a front surface plastic or stainless steel mirror?
...
Line up the PCB with the crosshairs and drill
...
OR use the 45 degree mirror without crosshairs and mount the scope to the mirror and post, then align the cross hairs to where the drill bit center is.
...
One could also modify a web cam or security cam or old video cam or ? to view things on a monitor

Yep. Lots of ways to do it. I'm currently liking the video/web/cam thing, and just taping cross hairs on the monitor.

The real trick is getting the drill to come up from the bottom to where you've aligned the hole location. Anything that does that works. In fact, you COULD dispense with the microscope entirely and simply stretch two very fine wires across above the PCB and use your eagle-eye super-vision to align it with no optics at all. My fat fingers would always be breaking the wires, though.

I stuck this up here to motivate the discussion. Seems to be working.   

[R.G.]

Just as I hit "submit" I went "Oh, wait! Laser pointer/crosshairs like on my chop saw!!"

[woody alien]

I've used a spot light to create a shadow of the drill bit. Gives a hunch of the direction, where the drill is going.

Replacing that crosshair with a laser beam is a good idea.

Although pocket size laser pointers are nowadays quite cheap, the optical elements, that would be required to make usable, and therefore tiny, say 0,5mm(0.01968") diameter laser beam,
are missing.

Industrial/military laser surplus anyone?   

[samhay]

Although pocket size laser pointers are nowadays quite cheap, the optical elements, that would be required to make usable, and therefore tiny, say 0,5mm(0.01968") diameter laser beam,
are missing.

If the laser pointer has a lens that roughly collimates the beam (go for blue or green focusing models), then all you need is a pin hole in the right place.

[R.G.]

There are some cross-hairs laser projector thingies I've seen, but I have no idea whether they're good enough for PCB drilling.

[GGBB]

This can be done with the stock Dremel table. Or it could back when I last bought a Dremel drill press, maybe 25 years ago. These things don't change much.

The one they sell now is different.  Not as good if you ask the internet.

Just as I hit "submit" I went "Oh, wait! Laser pointer/crosshairs like on my chop saw!!"

My drill press has those.  They work reasonably well, but the lines are not as sharp/thin as would make me feel they are precise, and the adjustment mechanism is poorly implemented so that it took me almost as long the set them up as it did drill my entire PCB the first time I tried it.  And it needs to be adjusted every time you change the table height.  But it works - I probably just need to get used to it a bit more.

[R.G.]

I did a quick look on line and there are crosshairs laser units available on ebay from $2 up to thousands per unit.

I'm guessing that there may be some variation in quality... 

In searching I got this funny feeling about staring into a laser pattern on reflective metal and focusing the spots really, really finely. Something about blind spots on my retinae. oops

I'm doing a bit more looking.

That crossed-wires thing looks better all the time.

[CodeMonk]

Dunno if this would work but....
1. Take a scrap piece of fiberglass or with an etched out pad.
2. Clamp it all down.
3. Drill the hole.
4. Position laser pointer UNDERNEATH until it goes cleanly through the hole. Some sort of holding jig would be needed of course. Maybe something with an X - Y Axis for fine tuning its position.
5. Put the board to be drilled into vise and position until you can see the laser through the un drilled pad hole. It would have to be off center in the vise though because of the big screw that tightens the vise.

You would also want to set your drill press depth so you don't drill into the laser pointer.
That way you can have it close to the board so you don't get a wide beam.
Hell, one of those cat toy pointers would probably be good enough.

[PRR]

Considering the Work is smaller than the Motor, it *may* make sense to fix-mount the motor and lower/raise the work platform.

If there's space in the workshop, you don't have to have a linear up/down. Especially on very small boards like stomp-guts. Hinge a piece of plywood to the wall and use springs or bungee-cord to support it sorta-level. A 20" platform and a 0.1" plunge is less than 1/3rd degree deviation from exact vertical, which is sure smaller than any hand-job or most press-jobs.

[R O Tiree]

...which is sure smaller than any hand-job...

Too many jokes, so little time...

But there's the issue of trying to hold the PCB firmly enough so it doesn't jiggle while you press down without depressing the platform while you re-position and therefore drill where you don't want to?

[R.G.]

5. Put the board to be drilled into vise and position until you can see the laser through the un drilled pad hole. It would have to be off center in the vise though because of the big screw that tightens the vise.

There's one fly in that ointment. The copper pad is completely opaque to laser light. You get zero show-through.

Works well if you drill from bottom and project a tiny, tiny spot.

Same worry issues about lasers reflecting from a focused spot onto retinae, even at low power.

[R.G.]

Lowering the board to the drill works OK, too, for drilling.

There are issues. Carbide bits are very, very intolerant of wobble. I had a Dremel that had a bad front end bearing and the runout would snap  the smaller carbide sizes. Could be the long lever arm cuts the radius of movement down enough. A big part of using a drill press or some such is to get the drill to move as close to along its own axis while drilling as possible.

The movement for our hobby drilling only needs to be tiny: 0.1"/ 2.5mm is plenty enough. But it needs to be as straight a movement as you can make happen. Very large radii of movement, several feet, are probably OK as long as the side-cutting action of the bit is as fast as the change in the hole alignment with the bit.

Hmmm. Maybe it's OK to use a single spot from a laser pointer, as noted above; or, failing that, a pointer that sits right on the top of the PCB. The problem with using a pointer or crossed  wires or some such is parallax. This is one reason that spotting holes with the drill bit itself is an issue. If the drill touches the surface to be drilled, and that's what you're using to do alignment, it's already cutting the surface if it's above the surface a few thousandths, your eye is seeing it as being in a place other than where it will drill. Our brains do some guessing about where it will really hit, and we do OK-ish until we get tired, blink, or sneeze. Mechanical pointers have the same problem, **except** that we can move our eyes to be directly above the axis of the drill's path, and thereby eliminate the parallax.

Optical means like microscopes with reticles, projected laser crosses and dots, etc. form the image on the surface of the material, completely eliminating parallax even if our eye in not right down the optical axis.

A laser dot as small as the hole is probably OK.

I found an assortment of laser crosshair projectors, but I also found an LED crosshair projector, which has the advantage that it's not coherent light, and doesn't have the burned-out-retina thing going for it.

Finally, I found an assortment of $20 USB video cameras and microscopes on ebay. These would probably do the job, but my experience is that they will have too much magnification. Anything over about 4x gets in the way because you can't easily see where the next hole is to be so you spend time wandering the PCB around to find the next drill location. A common usb surveillance camera might be just dandy if it will focus close enough.

A used linear bearing might be dandy for the movement of the drill. Just saying.

[davent]

Lee Valley sell an inexpensive flashlight stand with a magnetic base that looks like it would work well for holding and positioning the rifle scope mentioned in the first post.

http://www.leevalley.com/en/wood/page.aspx?cat=1,43456&p=62640


Now if the Dremel base wasn't aluminum it might be useful.

[CodeMonk]

5. Put the board to be drilled into vise and position until you can see the laser through the un drilled pad hole. It would have to be off center in the vise though because of the big screw that tightens the vise.

There's one fly in that ointment. The copper pad is completely opaque to laser light. You get zero show-through.

Works well if you drill from bottom and project a tiny, tiny spot.

Same worry issues about lasers reflecting from a focused spot onto retinae, even at low power.

Crap.
And I spent a few hours trying to figure out how to make the X - Y axis thing with crap and tools I have around here.
Back to the drawing board.

I do like your idea with the rifle scope and dremel drill press, but ATM, I'm broke and those things are out of my reach.
But that's been the story of my life, lack the funds to buy the proper tools, so I make my own Rube Goldberg contraption to get the job done.
Sometimes re-inventing the wheel can be educational.

Maybe I'll just hook the laser up to a Tesla coil and drill with that


Something I also gave some thought too and may have a solution for.
Or maybe its's totally stupid.

Most easily (read affordable) lasers have to wide of a beam to be useful for our needs.
Take a piece of flat board, Route out a pocket in the board a little more than 1/4 deep.
Cut a piece 1/4 aluminum to fit in the pocket that you routed in the board and secure it with some screws.
Remove the aluminum.
Clamp board the drill press table.
Drill a hole through the board, like with a spade bit, something wide.
Remount the aluminum.
Now, say you drill with a 0.5 mm drill bit, drill a hole in the aluminum 0.25 mm and use that hole to aim the laser.

Thoughts?

[davent]

Better at pictures then words so... so far inverted drillpress Dremel holder, swung my table-top drillpress table off to the side so it sits over the Dremel. Have an optical center punch i'm going to explore using it's sight, if that won't do it i'll try an ebay, generic, USB endoscope ( ~$15) or the rifle scope although i may be lacking headroom for the scope and my head.

[stallik]

Quote from: CodeMonk on Today at 03:44:52 AM
5. Put the board to be drilled into vise and position until you can see the laser through the un drilled pad hole. It would have to be off center in the vise though because of the big screw that tightens the vise.
There's one fly in that ointment. The copper pad is completely opaque to laser light. You get zero show-through. End quote

Copper may be opaque but there's no copper on the board where you want to drill provided you've etched first.

[CodeMonk]

Quote from: CodeMonk on Today at 03:44:52 AM
5. Put the board to be drilled into vise and position until you can see the laser through the un drilled pad hole. It would have to be off center in the vise though because of the big screw that tightens the vise.
There's one fly in that ointment. The copper pad is completely opaque to laser light. You get zero show-through. End quote

Copper may be opaque but there's no copper on the board where you want to drill provided you've etched first.

That's where I was going.
I always etch first.
And I can see a little bit of a glow through the etched parts with a normal LED flashlight.
I don't have a laser, but I'm probably going to go into town later this afternoon and plan on picking one up.
They only cost like $3.00 for the cheap ones.

Still trying to figure out how to do the X - Y Axis.
I need some All Thread.