Solid Wood Products 2623 



OTHER TEST DATA 



Hundreds of tests have been conducted to evaluate pallets, but conclusions 

 often differ and comparisons among tests are difficult. For example, Kurten- 

 acker (1969) concluded that in rough handling tests, pallets made of yellow- 

 poplar (a low-density species) tend to outperform pallets of hickory (a high- 

 density species). Stern and Dunmire (1972) found that while yellow-poplar 

 pallets, being lighter in weight than similar pallets made from hickory and oak, 

 initially resist a substantially greater number of impacts in revolving test drum 

 tests, the strength loss rate for yellow-poplar pallets is much greater than for oak 

 and hickory pallets. They concluded, therefore, that pallets made from oak and 

 hickory were usable substantially longer than similar pallets made of yellow- 

 poplar. 



LUMBER GRADES FOR DECKBOARDS AND STRINGERS 



The service performance of double-face stringer-type pallets is strongly de- 

 pendent on the impact strength of the end deckboards (on both upper and lower 

 decks) and on the strength of the stringers. To aid pallet users in specifying 

 pallets, the National Wooden Pallet and Container Association has published, 

 and periodically revises, descriptions of four grades of pallet parts termed 

 Precision, Premium, A A, and A in descending order of quality. Grades and 

 grading criteria are employed by industry to specify minimum quality accept- 

 able. Quality control is exercised by excluding parts containing unacceptable 

 defects. Readers interested in grading criteria should consult the Association for 

 current information. 



Below-grade pallet shook. — Permanent warehouse pallets generally require 

 use of parts which meet criteria for A-grade parts, as do heavy-duty expendable 

 pallets, designed to be used five or six times. 



To evaluate performance of one-trip expendable pallets, Wallin'^ — at the 

 request of pallet manufacturers — proposed a fifth grade which permits defects 

 not permissable in Grade A, and which are estimated to reduce the strength of 

 parts by 75 percent, as follows: 



Characteristic Grade 5 



Knots Average diameter to three-fourths width of piece 



Cracks Unlimited 



Splits/shake Unlimited 



Wane Not limited except nails not driven into or 



through wane 



Decay Up to one-half width in stringers. Not more than 



one nail per joint driven through the decay; no 

 nails driven into decay in stringer 



Slope of grain Unlimited 



Moisture content Unlimited 



Other defects Limited to the equivalent of those listed above 



^Wallin, W. B. 1979. Grading rules for below-grade pallet shook for expendable pallets and 

 quality standards and performance criteria for below-grade pallet shook for use in expendable 

 pallets. U.S. Dep. Agric. For. Serv., Northeast. For. Exp. Stn., Unpublished version of April 10, 

 1979. 



