A nail with a helical (spiral) thread that rotates as it is driven, giving more withdrawal resistance than a plain shank nail.
Detailed Definition
A drive screw nail has a threaded shank with a steep spiral, so it turns slightly as it is hammered or shot into the wood, much like a screw cut into the fibers. The thread locks into the wood and resists withdrawal better than a smooth shank nail of similar size. In the pallet industry these fasteners are usually called helical nails or helically threaded nails, and they are widely used to fasten deck boards to stringers and blocks, usually in collated form for pneumatic nailing machines.
Helical, annular and smooth shank nails
Pallet nails are generally grouped by shank type. Helically threaded nails have a spiral thread and rotate as they go in. Annularly threaded nails, often called ring shank nails, have a series of rings that grip the wood fibers. Smooth shank nails have no thread and rely on friction alone. Threaded nails usually hold better in withdrawal, which matters because loosened deck boards are one of the most common pallet failures.
How nail quality is specified
- Length, diameter and head size, chosen for the board and stringer thickness.
- Thread type and thread length along the shank.
- Stiffness, often checked with the MIBANT bend test and reported as a nail stress grade.
- Number and placement of nails per joint, set out in the fastener pattern.
Pallet design software accounts for fastener type when calculating joint strength, so changing the nail on an engineered design should be checked rather than assumed to be equivalent. Nails that split thin or dry boards, or that are driven at an angle and exposed, cause damage to product and are worth checking during incoming inspection.
Related Glossary Terms
Frequently Asked Questions
Is a drive screw nail the same as a screw?
No. A drive screw nail is driven like a nail, by a hammer or nailing tool, and its spiral thread makes it rotate as it enters the wood. A true screw is turned in with a driver and has a sharper, deeper thread. Drive screw nails hold better than smooth nails, but they are not designed to be removed and reused like screws, and they are much faster to install in pallet production.
Why do pallet makers use threaded nails instead of smooth nails?
Pallets are flexed, dropped, racked and hit by forks over their working life, which tends to work nails loose. Threaded nails, whether helical or ring shank, grip the wood fibers and resist being pulled out, so deck boards stay attached longer. Smooth nails are cheaper but are more likely to back out. Many pallet specifications therefore call for threaded nails of a stated size and quality.