Taper point drills were engineered to be used to pre-drill the pilot holes for the shank and threaded portion of a wood screw. The object, of course, is to use the proper size drills and drill to the proper depth to ensure the best holding power from the wood screw. This is critical when the fastened joints have to support a heavy weight or pressure such as when fastening planks to form the hull of a boat. A less critical application would be fastening a wood floor in a house or building cabinets.
The clearance hole though the wood being fastened should be as close to the diameter of the shank of the wood screw as possible. If the clearance hole is too small, the shank of the screw could bind in the hole, causing the screw to tighten before reaching its maximum pulling force in the wood being attached to or even breaking. If the clearance hole is bigger than the shank of the screw, the wood could move, which could cause squeaks, wear, and leaks. Space around the screw could also collect moisture, causing premature corrosion or rotting, depending on the materials involved.
The pilot diameter of the threaded portion of the screw is even more important. It determines how well the screw holds its grip on the wood it is being fastened to and how long it will maintain that grip. Generally, the diameter of the drill used to pre-drill for the threaded portion of a wood screw should be the same size as the root diameter of the screw. Wood screws are manufactured to various dimensions, which are listed in our Wood screw size chart.
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