Making pinholes isn't difficult. I recommend .002" brass shim stock, available in many hardware or perhaps auto supply stores. Aluminum is popular, but isn't as nice to work with. I've also used very thin stainless steel where small precise pinholes were needed, but it is difficult to work with. Measuring the size can be more difficult for some. Eric Renner's book gives several methods for this. For a perfectionist, pinhole diameter should be within five or ten percent of the design size. Pinhole photography is quite forgiving of imperfection. We do better when we concentrate on making the best possible photograph with whatever camera we use than when we merely concentrate on making or buying the best possible camera.
Originally Posted by yeknom02