Is Pre-drilling Required for Inclined Screw Applications?

When fully threaded screws are inclined to the wood surface, additional measures may be required in order for the screw tips to bite into the wood and initiate the self-tapping mechanism.

Fully threaded ASSY® self-tapping screws are designed to tap their own hole as they are driven into place. In cases where the screws are 90° to the wood surface, the screw tips bite into the wood, allowing the threads to engage and draw the screws in.

Although partially threaded screws tend to bite into the wood at an angle because of the more pointed counterthread tip, fully threaded screws will tend to travel across the surface just like a drill when inclined to a flat surface. There are two options to initiate the installation of inclined fully threaded screws:

  • Pre-drill pilot holes at the appropriately specified diameter
  • Manually adjust the screw angle once the threads are engaged

ASSY® 45° pre-drill jigs are recommended for steel-to-wood connection applications to facilitate the use of 45° washers. ASSY® 45° pre-drill jigs not only facilitate workflow–they also create precise 45° angles for the pilot holes at the correct locations in the wood members so that the screws line up with the washers. Custom site-made jigs made from metal or wood may be used for other applications. Suitable pilot holes are only required to set the angle and initiate installation, and so are only a few inches deep, even for long screws.

The second method involves initiating short holes using the screws at 90°. Once the threads engage the wood enough to hold the screws in place, the angle of the screws is manually adjusted, usually by referencing a triangular framing square. With the angle established, the self-tapping mechanism is then employed as the screws are fully installed.

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