You can buy laser drilled pinholes these days and frankly they are awesome. Go and speak to James at Reality So Subtle if you need some. Sometimes though, when you’ve made a pinhole camera out of a biscuit tin or a book or a roast duck or whatever, I really don’t need that kind of accuracy, so I make my own. Quickly here I’ll outline how I do it.
You need a piece of thin tin, a coke can or similar is ideal, a pin, a set of micro drill bits and some light grit sandpaper. The drill bit is not used to make the pinhole but rather test the size later. These can be bought in many sizes. Take the square of tin and gently press the pin onto the surface. Aa self healing cutting mat is ideal to do this on as it will stop you damaging your nice dinner table… Press very lightly and you’ll start to notice a high spot on the reverse of the tin. Take your sandpaper and sand this high spot until it’s gone. Again press the pin creating another high spot and then sand. Repeat this process and eventually you’ll create a tiny pinhole. Sanding the metal obviously makes it thinner and through testing I have found that there is a correlation between the thinness of the metal and the sharpness of the image. Take your micro drill bit and try and pass it through the hole. Keep sanding and using the pin until you can pass your drill bit through the hole, then you’ll know that you’ve got a pretty accurate pinhole size and shape.