I quickly calculate proper tap-drill diameters using this simple formula. Tap-drill diameter equals nominal diameter minus thread pitch. For example, drill size for a 3/8-16 thread is 0.375 0.0625 ...

If you already own a set of SAE drill taps, you can augment them with this five-piece metric set in M4, M5, M6, M8, and M10 sizes rated for both impact drivers and drills. Drill Tap Best Practices ...