predrillen

Predrillen, or pilot holes, is the practice of drilling a small hole before inserting a screw or other fastener. The technique is used in woodworking, metalworking, and masonry to guide the fastener, reduce material splitting, and improve driving accuracy and holding power. The term is common in many languages, including Norwegian.

In woodworking, predrilling helps prevent splitting near edges and in hardwoods. The hole diameter should be smaller than the screw’s outer thread diameter, so the screw can cut its own mating thread. The hole depth is typically slightly shorter than the screw length to allow full thread engagement. For softwoods, pilot holes are often about 60–70% of the screw’s outer diameter; for hardwoods, they may be larger to reduce splitting. Common drill bits include wood bits or brad-point bits. Countersinking is used for flat-head screws to sit flush with the surface, sometimes with a separate countersink bit.

In metal and other materials, pilot holes prevent work hardening and facilitate alignment and threading. Use appropriate drill bits for metal (often high-speed steel) and apply lubrication if needed. For masonry, pilot holes with masonry bits are used when anchors or plugs are required, rather than standard wood screws.

Benefits of predrilling include easier driving, reduced risk of splitting, and improved accuracy. Drawbacks occur if the pilot hole is too large, reducing holding strength, or when materials are very soft where predrilling is unnecessary for small fasteners. Overall, predrillen is a common, practical step in achieving reliable fastener connections.