Homebrew PCBs

I uploaded a picture of my laptop drill press to the photos section.

Mr. Moderator, maybe you can move that picture, and the following
text, to the files section.  (I couldn't upload to the files section.)

The drill press shown in LaptopDrillPress.JPG was built for drilling
small PC boards.  Total cost was less than $100 and it was built in
an afternoon.

I thought a lot about how to aim the drill accurately.  I tried
mounting a rifle scope to the front of a Delta drill press with a 10
inch throat.  That didn't work very well because there wasn't much
magnification obtained from the scope, and because it was hard to
judge the position front-to-back where the drill would land.

My conclusion was that the cheapest/best aiming solution was just to
be able to get my face up close to the axis of the drill bit and be
able to easily move my head around to view from different angles.
So I built the device shown in the picture.

The black platform is cut out from a 5-inch floppy disk carrying
case.  The main reason for using that was that it provided a plastic
hinge that bends in one axis without any play/slop/unwanted movement
in other axes.  The platform can twist (become non-planar) a little
bit, but that doesn't cause enough of a problem to bother fixing.
If necessary, the platform could be stiffened by glueing a board
underneath it.

The drill motor is a battery operated Craftsman.  The gray plastic
band that holds the drill onto the wooden arm is a conduit mounting
strap, a molded plastic part used to attach electrical conduits to
walls or ceilings.  A drill press with a hole saw was used to drill
out a semi-cylindrical cavity on the end of the wooden bar, to hold
the drill motor.

To use the drill press, I put it in my lap, hold and position the
PCB on the platform with my thumbs, and pull up on the platform to
drill a hole.  The accuracy is quite adequate for drilling pads for
integrated circuits.  I use a #60 high speed steel drill bit.  I
haven't tried a carbide drill bit.

How much error is caused by having the platform tilt instead of move
linearly along the drill axis?  Say the drill is 5 inches from the
hinge in the platform, and say the platform is raised about 1/8 inch
to drill a hole.  Then the platform rotates 1/40 radian.  For small
angles, 1 - cos a ~= a^2 / 2.  So the error (elongation of the hole)
due to tilting is about 5 * (1/40)^2 / 2 = 1/640 inch, about 2 mils.
Since I adjust the drill "by eye" so that it is perpendicular to the
platform, the error caused by misadjustment is probably similar or
greater.

Cheers,
- Jan Kok

I was so impressed with your Laptop Drill that I made a tabletop 
version. (I told ya I liked it!)
Elegant simplicity...


I put a 12" X 15" base and table on mine; complete with non-skuff 
feet.
There's a photo in the photo section.

There's a simple stopper block attached under the 12" arm.
It has a small slot cut in the bottom of the stopper with a dowel 
rod connecting to the Lifter/Lower arm. 
A simple cam made from a plastic toy wheel was glued to the dowel. I 
sanded it flat on one side to provide cam action for gravity feed 
and lift clearance. (About 1/4")
The slot in the bottom of the stopper allows you to completely lift 
the arm to change bits.
The retainer for the Dremel is an old scrap of Chimney-Mount antenna 
strap, connected to a 1/4" tension screw using an angle bracket and 
square nut.
I cut a V-Slot in the end of the arm using a hand held jig-saw. Not 
very accurate on verticals so I used a sliver of cardboad to shim 
the Dremel true vertical.
I added 1/8" holes at the back to organize my small carbide bits.

The whole project took only a day.
Cost was $0.00 not counting the Dremel or bits. Made from all scrap 
stuff on hand.
Other scrap used includes a 2x4 and 1x2 boards, a small piece of 
plywood, (2) 1/4" x 3 1/2" bolts w/ wingnuts, finish nails, 4 screws 
(in back uprights), and glue.

It works great on my single boards, and the arc that the Dremel 
travels is not a problem. It's too slight.

Thanks again for the great idea + photo, jankok !

Byron



--- In Homebrew_PCBs@yahoogroups.com, "jankok5" <kok@s...> wrote:
> I uploaded a picture of my laptop drill press to the photos 
section.
> 
> Mr. Moderator, maybe you can move that picture, and the following
> text, to the files section.  (I couldn't upload to the files 
section.)
> 
> The drill press shown in LaptopDrillPress.JPG was built for 
drilling
> small PC boards.  Total cost was less than $100 and it was built in
> an afternoon.
> 
> I thought a lot about how to aim the drill accurately.  I tried
> mounting a rifle scope to the front of a Delta drill press with a 
10
> inch throat.  That didn't work very well because there wasn't much
> magnification obtained from the scope, and because it was hard to
> judge the position front-to-back where the drill would land.
> 
> My conclusion was that the cheapest/best aiming solution was just 
to
> be able to get my face up close to the axis of the drill bit and be
> able to easily move my head around to view from different angles.
> So I built the device shown in the picture.
> 
> The black platform is cut out from a 5-inch floppy disk carrying
> case.  The main reason for using that was that it provided a 
plastic
> hinge that bends in one axis without any play/slop/unwanted 
movement
> in other axes.  The platform can twist (become non-planar) a little
> bit, but that doesn't cause enough of a problem to bother fixing.
> If necessary, the platform could be stiffened by glueing a board
> underneath it.
> 
> The drill motor is a battery operated Craftsman.  The gray plastic
> band that holds the drill onto the wooden arm is a conduit mounting
> strap, a molded plastic part used to attach electrical conduits to
> walls or ceilings.  A drill press with a hole saw was used to drill
> out a semi-cylindrical cavity on the end of the wooden bar, to hold
> the drill motor.
> 
> To use the drill press, I put it in my lap, hold and position the
> PCB on the platform with my thumbs, and pull up on the platform to
> drill a hole.  The accuracy is quite adequate for drilling pads for
> integrated circuits.  I use a #60 high speed steel drill bit.  I
> haven't tried a carbide drill bit.
> 
> How much error is caused by having the platform tilt instead of 
move
> linearly along the drill axis?  Say the drill is 5 inches from the
> hinge in the platform, and say the platform is raised about 1/8 
inch
> to drill a hole.  Then the platform rotates 1/40 radian.  For small
> angles, 1 - cos a ~= a^2 / 2.  So the error (elongation of the 
hole)
> due to tilting is about 5 * (1/40)^2 / 2 = 1/640 inch, about 2 
mils.
> Since I adjust the drill "by eye" so that it is perpendicular to 
the

> platform, the error caused by misadjustment is probably similar or
> greater.
> 
> Cheers,
> - Jan Kok

--- In Homebrew_PCBs@yahoogroups.com, "starsnstripes_2003" 
<bwatson@a...> wrote:
> I was so impressed with your Laptop Drill that I made a tabletop 
> version. (I told ya I liked it!)
> Elegant simplicity...

Nice pic, and it looks good.

I thought about the unit and if I were to modify it, I would add an 
articulating arm magnifying light to see the hole locations better, 

AND....

I would add a foot operated lever.  spring load the lever so when you 
stepped on it, the drilling arm drilled the hole and only the spring 
pulled the dremel, not the power of your foot.

alternatly, mount a solenoid and a foot switch.

now, to design a fast change chuck for a Dremel.......

Thanks for the ideas, Dave ;-)


I already had thought about a simple footswitch, But it would only 
turn on the Dremel. 
MCM? or Mouser? has a footswitch with phono plug for about $7.00.
I can mount a phono jack in a cheap power strip and plug the 
footswitch into it to enable foot operation for the whole power 
strip. I think Dremel gets about $45 for their footswitch...Ouch!

You don't need the spring to pull down on the Dremel. You might need 
it to provide counter-balance for a true-gravity feed, though. 
Gravity does the job fine. (Adjust the pivot bolt just snug enough 
to remove "play" in the arm). I used a little melted candle-wax to 
lubricate the pivot points.
The feed arm on mine has the feel of a regular drill press with just 
about 80 deg. arc providing the full 1/4" travel. Works just fine 
for my purposes :-)

I chuckled with your suggestion of an auto-tool changer! I came from 
a CNC production environment with over 500 various CNC machine tools.
Most had tool changers. They are a pain in the A$$...(I was CNC 
Maintenance Leader there.)
My Dremel set came with Hex and Knurled collet nuts.
The knurled collet nut allows pretty fast changes just using "finger-
tight" if you stick to the Carbide drills with 1/8" shanks. They are 
only about $4.25 for a pack of 5 (resharpened) at Drill Bit City.

As for auto-feed and retract, I suppose if you were really serious, 
you could mount a stepper motor w/controller to a modified feed arm, 
and provide a limit / microswitch to do the retract.

Not sure if the solenoid would work, but it might if you let the arm 
free-fall and the solenoid do the lift.

I'm not THAT serious, though!

Well, maybe if I find an old printer that I can scrap...Hmmm...So 
much fun in such a small Yahoo Group! 
Next up: X/Y Table ?


--- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha" <dave_mucha@y...> 
wrote:
> --- In Homebrew_PCBs@yahoogroups.com, "starsnstripes_2003" 
> <bwatson@a...> wrote:
> > I was so impressed with your Laptop Drill that I made a tabletop 
> > version. (I told ya I liked it!)
> > Elegant simplicity...
> 
> Nice pic, and it looks good.
> 
> I thought about the unit and if I were to modify it, I would add 
an 
> articulating arm magnifying light to see the hole locations 
better, 
> 
> AND....
> 
> I would add a foot operated lever.  spring load the lever so when 
you 
> stepped on it, the drilling arm drilled the hole and only the 
spring 

> pulled the dremel, not the power of your foot.
> 
> alternatly, mount a solenoid and a foot switch.
> 
> now, to design a fast change chuck for a Dremel.......