A coworker bought a view camera, and while searching for glass wants to
take some pinhole pictures. I ran through the formula, and the pinhole
needs to be about .025". I have, somewhere, PCB drill bits in that size
range. The material will be brass shim or soda can. My first attempt was
going to be taping the Dremel to the quill of the drill press and go for
it. Anyone have better ideas for a clean burr free hole?
On Sunday, December 2, 2012 1:53:33 PM UTC-8, axolotl wrote:
Get a bit of aluminum foil, fold into a stack with many layers (16 is good).
Stab the center of the stack with a pin.
Peel off layers of the stack until the hole size is right.
Mounting the foil, and protecting it, is left as an exercise.
On Sun, 02 Dec 2012 15:11:41 -0800, anorton wrote:
I dunno -- the pinhole pictures that I've taken were done in a home-made
camera (cardboard with lots of black paint and electrical tape) exposing
onto B&W print paper. Pinholes were made with a pin and aluminum foil,
and boy I wish I had know the "stack the foil" trick!
For a hand-made pinhole -- even with a pin in tin foil -- the blur spot
is going to be roughly the size of the pinhole. The exposure times --
even with real film -- are long. So a small hole is good for crisp
pictures, and you're going to have to have the camera firmly mounted
during exposure anyway.
If you want better support, make a blank out of the material of choice to
fit the camera, drill a 1/4" or so hole in the center, then tape the foil
to the blank with electrical tape. That'll give you durability, while
still leaving you with a nice tiny hole in the tin foil.
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
As an optical engineer, I have actually done this a many times for various
reasons. You do not really need the Dremel. Just use the drill press on its
highest speed and very light pressure. The drill press should be small
enough to control the force very finely. Those small carbide bits break
very easily. Certainly if you just tape the dremel to the quill, it would be
hard to keep the bit perpendicular which is probably important to keep it
I have had good luck clamping the shim stock between two sheets of aluminum
with about a 1/8" hole drilled in the top piece for clearance.
Another, much easier, method I have used is to place the shim on a wood
backer and press in the point of a compass or divider. I measured the height
on the compass point that gave me the diameter I wanted, marked it, and
pressed in up to that point. This leaves a rim of deformed metal on the
back side which has a slightly smaller I.D., so I turn it over and repeat
from the backside. The rim is not usually a problem, but if you want to get
rid of that, you can press on the back side with a larger angled cone tip.
You can also try removing it by hand-twisting a larger drill bit from the
Another method I have tried to get accurate holes is to open a (old) dial
caliper to the appropriate size, lock it, place the shim over the gap
between jaws, then press in the compass point until it is wedged in the gap.
I am not sure this is better, though, because the rim on the back side tends
to get unevenly deformed.
After thinking about this just now, it occured to me that there might be a
better procedure I want to try: Start a small hole with a compass point and
wood backer. Then, flip the shim over and finish to the final size on the
calipers. Enlarging the small hole from the backside will probably spread
the rim open rather than push it through onto the calipers where it
otherwise would be deformed.
Mill the hole, don't drill it. You should be able to find an end mill
that size fairly easily. I think I have one in the sets I got from
Gunner, complete with 1/4"(?) holders.
Otherwise, maybe use a drill press and drill it, flip it over, run a
chisel over the burr, flip it and drill; repeat until perfect.
Question: How do these mfgrs -make- bits that small, anyway?
...in order that a man may be happy, it is
necessary that he should not only be capable
A 25 mill is a monster pcb mill if you are making high speed stuff.
I used 7 and 10 mill endmills that were typically 2 and one was a 3
cutter. They are carbide and turn fast - 10k or more and must fly cut
Copper and fiberglass and epoxy matrix (and other exotic materials).
Small pcb drills are often sold in Dremel kits. They have the large ring
On 12/2/2012 4:55 PM, Larry Jaques wrote:
And the color of the ring tells you something about the size.
I'm not sure how many in the color sequence, but it is enough so
you can usually tell two of the same color ring but nearby sizes apart.
And the ones in kits for dremels (they all have 1/8" shanks) are
usually resharps -- I don't know how many times they will have been
resharpened but the glass boards even dull the carbide over time, so
they do go out to be resharpened, until they get too short for the CNC
machine driving them to accept them.
Since you have the drills the easiest method for you, in my opinion,
is to clamp the brass shim between two brass sheets at least 1/16"
thick and drill through. The goal is a round hole with no burrs and
drilling through the same material for both the wanted part and the
back up pieces will work well. One way of getting all the thin pieces
to stay very close together while drilling is to use some super glue
to bond them under pressure. Then use heat (BUT DON'T BREATHE THE
FUMES!) to release the part from the backup pieces. Spin the drill as
fast as possible. If you have a thick, say 1/8", piece of brass then
use that as the bottom piece and don't drill all the way through. This
will help prevent drill breakage. So clean the brass pieces, apply
super glue, stack the pieces, put a weight on the stack or clamp in a
vise, and after the glue has set drill the hole. You might as well
drill several holes at a spacing which would allow you to make several
apertures in case one gets damaged.
On 12/2/2012 5:14 PM, email@example.com wrote:
Can you do it with a liquid?
Drill a bigger hole. Solder in a 0.025" aluminum or stainless wire.
The solder won't stick to the wire. Not sure what surface tension will
do to the thickness, but would be easy to try.
One company uses a chemical etching process on very thin metal.
I'ved used hypodermic needles on gaffer's foil, which is just thick
blackened aluminum foil.
Other people have had laser drilled holes.
Poking a hole in foil is only as complicated as you want to make it.
pinhole cameras do not produce the best possible image, so trying to
acheive the perfect pinhole doesn't make any sense.
Maing the cone will be harder than the hole.
I have a set of oxy/acet tip drills that you would end up turning by
hand. I think that drilling the hole and "filing" with a tip cleaner
would give a good burr free hole. You would also get a more burr free
hole in brass or aluminum if you blunt the lead edge of the drill flutes
look at photos about half way down the page.
Make a dimple in the shim stock like this ____^____ and carefully file
the point until it breaks through, you end up with a hole with extremely
thin edges and no burs in a usefully thick metal surround.
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