Pilot hole

Plain-English definition

A pilot hole is a small, pre-drilled hole made in a material before driving a screw or nail into it. The drill bit used is usually slightly narrower than the thickness of the screw’s thread.

Why it matters

When you drive a thick screw into solid wood, the screw displaces the wood fibers, pushing them outward. Near the end or edge of a board, this outward pressure will cause the wood to split wide open. A pilot hole removes enough material to relieve this pressure while leaving enough wood for the screw threads to grip tightly. It also acts as a guide, ensuring the screw goes in straight.

Common mistake

A common mistake is using a drill bit that is exactly the same size as the screw. If the pilot hole is too wide, the screw threads will have nothing to bite into, and the screw will pull out easily. The ideal pilot hole is the diameter of the screw’s solid inner core, not including the threads.