Out of sight can mean out of mind, but out of mind isn’t necessarily a good thing regarding pallet nails. While the price difference between cheaper and more expensive pallet nails is modest, do you know that a better-quality nail can make a dramatic improvement in pallet quality? Without getting too technical, in this blog, we introduce some of the basics that can be useful for pallet buyers to understand.
Simply put, fasteners bind the wooden components of the pallet together. They include driven nails and staples, bolts, wood screws, and lag screws. Most pallets utilize one of two types of nails, including helically-threaded or drive-screw nails and annularly threaded or ring-shanked nails.
Helically threaded nails feature continuous spiral threads along the shank. Annularly threaded nails come with numerous rings along the shank that help grip the wood and prevent nail withdrawal. Of the pair, helically-threaded or drive-screw nails are the most popular choice for automated pallet assembly. Both types, however, are widely used by pallet manufacturers.
Annular nails offer better resistance to withdrawal and, for this reason, are often recommended for low-density hardwoods and most softwoods. Helical nails of the same gauge, though, provide better bending resistance and are therefore recommended for medium and high-density hardwoods. Bent nails can result in deck board splits, leading to the deck board being pulled through the nail head, a failure known as “pull-through.”
According to Virginia Tech, pallet joint failure is related to fastener withdrawal resistance and fastener shear resistance. Both of these damage factors are directly influenced by fastener quality. Withdrawal resistance speaks to the ability of the nails to secure the deck board to the stringer or stringer board and block and thus prevent separation of the deck board. According to Virginia Tech, fastener withdrawal resistance is most affected by wire diameter, the difference between thread diameter and wire diameter, and the number of helices per thread length.
Shear resistance, on the other hand, pertains to horizontal impact and displacement of the deckboard. Impact from forklift tines, for example, can drive a deckboard inward, pushing it away from the ends of the stringers.
The Morgan Impact Bend Angle Nail Test (MIBANT) is used by industry researchers and professionals to predict fastener performance in use. Fasteners are measured according to nail shank length and width, thread angle and type, as well as nail head size and shape. Fasteners are tested to determine how much force it takes to bend them and how much force it takes to pull them out after they’ve been driven into wood. The more force that is required to bend or pull the fastener, the stronger that fastener is, which helps contribute to a more durable pallet.
An article by Virginia Tech underscores the value of modest improvements in nail quality. To demonstrate the impact of fasteners on pallet quality, the authors compared the performance of 11.5-gauge bulk nails with 12.5-gauge collated nails in a standard GMA pallet usin Best Load™ pallet design software. Gauge refers to wire thickness, with the smaller gauge denoting a thicker nail.
Results demonstrated that pallets built with better quality 11.5-gauge nails exhibited considerably better durability than the 12.5-gauge. They lasted twice as many trips before needing repairs and twice the number of trips before being replaced. The pallets manufactured with 11.5-gauge nails exhibited lower damage rate values and relative damage severity. Based on results, the 11.5-gauge nails were determined to result in 85.6% more durable pallets than those built with 12.5-gauge nails while doubling pallet life.
Don’t take pallet nails for granted. When it comes to improving nail quality, a little investment can mean a lot. Fastener withdrawal resistance and shear resistance are both critical to pallet durability, and durability can be dramatically improved through the use of better-quality fasteners.
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