A spiral-shanked nail used in pallet construction for higher withdrawal resistance than smooth nails.
Detailed Definition
A helical nail, also called a spiral or helically threaded nail, has a shank rolled with a continuous spiral thread. As it is driven, the nail turns slightly and the threads cut into the wood fibers, so it resists pulling out better than a smooth shank nail of similar size. Helical nails are widely used in pallet assembly, often as coil nails fed by pneumatic nailers, and are typically made from hardened steel so they can be driven into dense hardwood without bending. The other common deformed shank type is the annular ring nail.
Why shank type matters on a pallet
Pallet joints are loaded in ways that try to pull deck boards off stringers or blocks: forks catching a board, loads shifting in transit and the wood shrinking as green lumber dries. Withdrawal resistance keeps boards tight through those cycles. Deformed shanks such as helical and ring shanks are preferred over smooth shanks for this reason, especially in pallets built from green lumber.
Shear strength and stiffness of the nail also matter. A nail that bends easily lets joints rack and loosen even if it does not pull out.
What to specify and check
- Nail length, wire diameter and head size suited to the board and stringer thickness.
- Shank type: helical or annular ring, with thread geometry from the fastener supplier.
- Hardness and bending resistance, which the pallet industry often measures with the MIBANT bend test and expresses as a nail stress grade.
- Number and placement of nails per joint, set out in the fastener pattern.
A common mistake is switching to a cheaper or thinner nail without updating the pallet design. Pallet design software such as the NWPCA Pallet Design System accounts for fastener properties when estimating strength and durability.
Related Glossary Terms
Frequently Asked Questions
What is the difference between a helical nail and a ring shank nail?
Both are deformed shank nails designed to hold better than smooth nails. A helical nail has a spiral thread that makes it rotate slightly as it is driven. An annular ring nail has a series of separate rings around the shank that lock into the wood fibers without rotating. Each performs well in pallets; the better choice depends on wood species, density, moisture and the fastener supplier's test data.
Are helical nails the same as drive screw nails?
The terms overlap. Drive screw usually refers to a nail with a steep helical thread that turns noticeably as it is driven, while helical or spiral nail can describe threads of various pitches. Suppliers name products differently, so compare the actual thread geometry, wire diameter and hardness rather than the label when choosing pallet fasteners.