What screw length should be used when fastening ductwork with screws?

What screw length should be used when fastening ductwork with screws?

• A. Screws about the same length as board thickness.
• B. Screws that are at least half inch longer than board thickness.
• C. Screws shorter than board thickness.
• D. Nail-like fasteners

Answer: (B)

When fastening ductwork, you want enough screw length to bite into the backing material beyond the duct flange, giving a solid hold. Using screws at least half an inch longer than the board thickness ensures the threads engage into the support and resist pull-out and vibration, rather than just sitting on the surface. If screws are about the same length as the board thickness, they can bottom out or fail to gain solid engagement, leading to a weak hold. If they’re shorter than the board thickness, they won’t reach the backing material at all, again reducing grip. Nail-like fasteners don’t provide the threading and withdrawal resistance needed for secure duct connections.

When fastening ductwork, you want enough screw length to bite into the backing material beyond the duct flange, giving a solid hold. Using screws at least half an inch longer than the board thickness ensures the threads engage into the support and resist pull-out and vibration, rather than just sitting on the surface.

If screws are about the same length as the board thickness, they can bottom out or fail to gain solid engagement, leading to a weak hold. If they’re shorter than the board thickness, they won’t reach the backing material at all, again reducing grip. Nail-like fasteners don’t provide the threading and withdrawal resistance needed for secure duct connections.