Wood Screw Drill Bit Size

Wood Screw Drill Bit Size

How do I know what size drill bit to use for wood screws? Is there a hidden code someplace on the package, or is this something you are supposed to just know?

Andy Rae: When pre-drilling holes for screws, there’s a rule of thumb that comes in two parts: In softwoods, pick a bit that’s the diameter of the root of the screw, which is the shank area just below the screw threads, and not the shank portion directly below the screw’s head. In hardwoods, pick the next bigger size, or about one sixty-fourth of an inch larger.

Stephen Rosasco: I hold my drill bit up to the screw and try to match the bit to the inner diameter of the screw. That’s the core without the threads.

Mike Van Pelt: Go visit www.wlfuller.com Fuller manufactures counterbores, plug cutters, taper point drills and brad points made in the USA. Request a catalog. It is jam-packed full of information and recommendations for wood screw pre-drill size and length.

Carol Reed: Just measure the “valleys” of the thread. Calipers are a great tool for this task.

Richard Jones: Traditional screws with a tapered shank need two holes: a clearance hole through the upper piece of wood and a pilot hole in the lower piece for the screw threads to bite into. The clearance hole lets the screw pass through without the threads biting. You can also buy taper drills and step drills that will replace or replicate the holes I described.

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