What size drill bit for 1/4 20 tap?

When tapping a hole for a 1/4-20 thread, it's common to use a drill bit that is slightly smaller than the tap size to accommodate the threads. For a 1/4-20 tap, the recommended drill bit size is typically a #7 drill bit (0.2010" - 5.105mm).

Therefore, you would use a #7 drill bit to drill the hole before tapping it with a 1/4-20 tap. This allows the tap to cut into the material and create threads without removing too much material, providing a better fit for the screw or bolt that will be threaded into the hole.