This is how I make my pinholes ...
I use stiff copper sheet, cut to the size of a plastic 35mm slide mount. Create a dimple on one side with a ball-point pen by pressing down lightly against a piece of soft wood. Then, using what I think is an Arkansas oil stone (it's pretty fine) abrade the bump gently until a 1mm circular abrasion appears. This makes the bump thinner for the needle. They were difficult to find but I got some numbered needles - mostly I use a #13 which is 0.3mm dia.
Carefully rotate the needle point against the inside of the depression - this is where you'll make burrs if you push in too roughly. The drilling motion is a bit like trying to light a fire, only real slow. Once the tip is through you should only go a short way up the 'cone' end of the needle, don't go right through - the hole is probably already bigger than the needle diameter, so stop. Carefully abrade the bump side again - and then put it on the scanner. Check the diameter in mm under Image Size.
If it's not a circle you can try again gently with the needle. If the hole's too big - throw it away and do another.
Fit to slide mount, use a black felt tip pen in the area immediately around the hole and black paint over the back of the rest of it. Tape the mount onto your box camera.
Alternatively, if you're using an old folder camera, remove the lenses from the old shutter and cut the copper sheet into a circle to fit behind the aperture leaves.
E Voila! Start shooting.
