Crook and overlength in hardwood lumber:results from a 14-mill survey
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Forest Products Journal. 53(5): 61-66.
Data on red oak lumber were collected at 14 furniture and cabinet industry rough mills to identify how crook and overlength are related to lumber grade and size from mill to mill. The amount of crook in a sample of dry, 4/4 thickness, red oak lumber was significantly influenced by lumber grade and length, supply region, and mill. There were no differences in crook based on board width. Average overlength, which can pose challenges in lumber drying operations, was influenced by lumber grade, nominal lumber length, source region, and supplier. There were several complex interactions between these variables that are important in modeling overlength. Odd-length lumber, which accounted for 13.7 percent of the lumber sample, generally is trimmed less precisely than even-length lumber. There was no consistency between lumber grade and overlength from mill to mill. In some cases, the 3A grade had the highest average overlength; in other cases, the FAS, Selects, 1 Common, or 2 Common grade had higher overlength. Average log overlength amounts are higher than lumber overlength amounts. Secondary manufacturers who incur increased costs due to overlength lumber or decreased yield due to crooked lumber need to look for these differences in their own lumber supply and learn how they reduce their mill's processing efficiency and yield.
Wiedenbeck, Jan; Brown, John; Bennett, Neal. 2003. Crook and overlength in hardwood lumber:results from a 14-mill survey. Forest Products Journal. 53(5): 61-66.