Do you have a picture of the setup?
_____
From:
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com]
On Behalf Of Charles R. Patton
Sent: Thursday, June 09, 2011 6:33 PM
To:
Homebrew_PCBs@yahoogroups.comSubject: Re: [Homebrew_PCBs] Precision Drilling of PCBs
I have an old small miniature precision drill press. I drilled a 3/8"
hole on centerline with the drill bit and cut a pocket in the underside
of the base plate and put a piece of 1/8" thick plastic in the pocket.
The plastic also has a 3/8" hole in line with the baseplate. I lined
the hole in the plastic with 3 white SMT LEDs cocked to throw their
light up through the hole. Next I took a cheap ($10) webcam that has a
lens that can be hand adjusted to focus at about 1/2" (Just keep
screwing it out until it focuses on a board placed on the top side of
the base.and pressure loaded it into place with a spring loaded clamp
(made from 1/2 of a small desk fan clip-on clamp.) There is still a
problem in that the "boresight" will be likely be twisted in relation
to the flat of the lens. I.e., when you look at the drill come down
toward the lens, it will look like it is coming from one side or
another. The solution I arrived at to circumvent that (as I tried to
physically adjust it, and it was just too much of a pain) is take a
vacuum formed transparent carton of about 0.010" thick sheet such as
sold in the grocery store that contains fruit like tomatoes, cherries,
strawberries, etc. Cut out a clear, un-molded portion (typically in
the lid) and preferably about twice as big as the board you want to
drill. Tape it on the top side of the baseplate with a clear section
over the 3/8" hole the camera is looking up through. Set the drill to
down stop just after drilling through this plastic (so you don't hit the
lens below) and drill a hole with your smallest intended drill. Now,
although the drill moves through the image, the hole in the plastic is
fixed and exactly where the drill will be. Put your PCB with the traces
face down on the baseplate and center a spot you want to drill in the
center of that hole. Drill. You' can easily drill within 0.005" or
even better if you want to take the time, with no problem. The 3/8"
view allows you to see traces around the hole and allow you to know
where you are on the PCB.
The particular web cam I used was a"Gear Head" unit that comes with
AmCap software. It is fairly low resolution, and noisy, but it has in
addition to the screw lens with enough throw to focus close, the
capability of having the left-right, up-down reversed in the AmCap
software. So when I slide the PCB left, the image moves left. This
definitely makes like easier.
Regards,
Charles R. Patton
. On 6/9/2011 1:16 PM, Bruce Parham wrote:
>
>
> > Hello Group
> >
> > I have a quick question about precision drilling of home made PCBs.
> >
> > Because of poor eyesight, I use a CCD microscope next to my Dremel
> > Model 300 drill press stand. Although this set up is a big improvement
> > over doing thing solely 'by eye', there is a parallax error introduced
> > between the location of the retracted drill tip and where it
> eventually comes in contact with the PCB. Once I saw a milling machine
> where one
> > was able to sight straight down into a bulls eye. Is there a way to
> > rig mirrors to do this?
> >
> > P.S. Sincle sided boards are no problem, as I can hold them up to
> > strong light and position a hand held rotary tool with good enough
> > accuracy.
> >
> > Any suggestions would be appreciated.
> >
> > Cheers
> >
> > Chris
> >
> Hi Chris,
>
> You might try to find a metallic first surface mirror that you can
> drill a small hole into on a 45 degree angle
> and mount onto your drill stand with the drill bit going through the
> hole. Position the camera so it looks into
> the mirror from the side and down the drill via the mirror.
>
> A less elegant method is to use two point source lights (small halogen
> desk lamps) mounted 90 degrees apart
> and pointed toward the drill tip. As the drill tip approaches the board,
> the shadows will converge on the target.
>
> Bruce
>
>
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