Homemade Flathead Screwdriver

This makes a quality and efficient driver bit. On occasion where I need an odd bit, quick results are had by milling both sides of center-line against a four flute endmill. This produces a parallel form instead of a wedge. A simple calculation reveals the offset needed to generate thickness desired. If you have indexing tools, that allows conventional milling on both sides. Basic figures needed: rod diameter minus bit width plus 1/2 cutter diameter. Generally the 'length' of cut is about 2x depth of slot. Many assemblies have uniquely sized slots, especially shotguns. When a vintage example is engraved, all manner of precautions are taken to preserve that fastener.