Pallet manufacturers and recyclers can distinguish themselves from competitors by choosing nails that improve pallet quality, do a better job of protecting a customer’s product, and reduce the per-trip cost of the pallet.
“The fastening system is an inexpensive way to dramatically separate your product from the competition,” said Marshall “Mark” White, former head of the Virginia Tech Center for Packaging and Unit Load Design and the university’s William H. Sardo Jr. Pallet and Container Research Laboratory.
“The range of fastener quality available for pallet assembly represents a 10-fold difference in resistance to rough handling and pallet life,” added White, who continues to work on a part-time basis at Virginia Tech and also has his own consulting business, White & Company.
White recommends annularly-threaded or ring-shanked nails for low-density hardwoods and most softwoods because they have better withdrawal resistance. Helical nails of the same gauge have better bending resistance, and they are recommended for medium- and high-density hardwoods.
Pallet joints fail two ways. The nail head may pull through the deck board (nail head pull-through), or the nail shank may pull out of the stringer or block (nail shank withdrawal failure). Nail head pull-through typically is caused by the bending of the nail and the resulting splitting of the deck board.
Of all the characteristics that impact the quality of helically-threaded nails, the two most significant are the difference between wire diameter and thread-crest diameter, and the bending stiffness of the nail, explained White. The difference between the thread-crest diameter and wire diameter, which is directly related to the thread depth and the angle of the thread, are the characteristics that most affect nail shank withdrawal failure.
A general rule to remember, the greater the difference between nail wire and thread diameter, the greater the quality of the nail and its resistance to shank withdrawal. In fact, thread-crest diameter is one of the most critical nail characteristics that affects withdrawal resistance.
If the difference between nail thread and wire diameter is more than 0.020 inches, relative nail quality is excellent. When the difference drops to 0.016 to 0.020 inches, relative nail quality drops to good. A difference of 0.012 to 0.015 inches is marginal, and less than 0.010 inches is considered poor.
For helically-threaded nails, thread angle also is a key characteristic impacting withdrawal resistance. Thread angles of 67 to 68 degrees are typical. Thread angles of 77 degrees or greater are typically called ‘lazy’ threads and are of poor performance.
One measure of bending resistance in nails is known as the MIBANT angle, which is measured by a MIBANT (Morgan Impact Bend Angle Nail Tester) testing device. The MIBANT angle of most pallet nails ranges from 8 to 46, with the lower the angle, the greater the quality of the nail.
A MIBANT angle of 8-24 degrees is considered excellent for relative fastener quality; 25-35 degrees is good, and 37-46 is acceptable. A nail with a MIBANT angle greater than 60 degrees is much lower quality and only acceptable for clinch nailing for deck board and stringer board joints in block-style pallets.
Keep these principles in mind when making your nail selection. A better nail can produce a better pallet. Check out the nails offered by the quality suppliers listed in this guide.
