Solid Wood Products 2633 



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Figure 22-36. — Three- by 0.120-inch pointless, helically-threaded, hardened-steel pal- 

 let nail with thin-rimmed umbrella head; the four flutes have a thread angle of 63 

 degrees. 



Performance of pallet nails in 22 pine-site hardwoods. — The effectiveness 

 of these nails (fig. 22-36) was evaluated in deckboard-stringer joints by E. G. 

 Stem (1976). Twelve deck-board stringer joints for each of the 22 species were 

 assembled with a single nail from green lumber and tested after several weeks 

 equilibration at 70°F and 50 percent relative humidity. Forces required to pull 

 the nailhead through the deckboard and to withdraw the nail shank from the 

 stringer were measured. Moisture content at test was 10 to 12 percent. Speci- 

 mens for the test came from the same lumber associated with data in table 22- 1 3 , 

 in which specific gravities are tabulated. 



Pull-through resistance of the nailhead, which averaged 1,129 pounds (table 

 22-15), was minimum in yellow-poplar (704 pounds), sweetgum (820 pounds), 

 and sweetbay (845 pounds); it was maximum in winged elm (1 ,407 pounds) and 

 mockemut hickory (1,311 pounds). 



Shank withdrawal resistance, which averaged 1,198 pounds (table 22-15), 

 was minimum in yellow-poplar (628 pounds), black tupelo (923 pounds), and 

 sweetbay (998 pounds); it was maximum in northern red oak ( 1 ,522 pounds) and 

 mockemut hickory (1,437 pounds). 



For these nails, forces (in pounds) were loosely correlated to wood specific 

 gravity based on ovendry volume and weight (G), as follows: 



Nail-head pull-through resistance = 1,857G (22-1) 



Nail-shank withdrawal resistance =3,801G^^ (22-2) 



Readers needing to relate withdrawal forces per inch of nail penetration to nail 

 type, and nail-head pull-through resistance to nail-head area are referred to 

 figures 24-7, 24-8, and 24-19 of Koch (1972). 



Nailing standards. — When wood species of different densities are used for 

 the construction of wooden pallets, different sizes and numbers of nails are 

 needed to assemble pallets of comparable strength. Wallin and Stern (1974), in a 

 tentative nailing standard for warehouse and exchange pallets, suggested that for 

 optimum performance, only hardened-steel nails, 3- by 0. 120-inch be used for 

 mixtures of soft, medium, and dense species, and that all nails be helically 

 threaded with a thread angle of about 60 degrees. For dense species only, they 

 recommend I-Va- by 0. 1 10-inch nails; for mixtures of dense and medium dense 

 species (e.g., pine-site hardwoods), they suggested 2-/2- by 0.120-inch nails. 



