The effect of crook on yields when processing narrow lumber with a fixed arbor gang ripsaw

Today’s hardwood lumber resource is narrow (under 7 in. in average width) and 22 percent of all kiln-dried boards may have 1/2 inch or more of crook or side bend. This could present a serious obstacle to the adoption of gang-ripping as the initial lumber breakdown step. Among the negative effects of crook found in this study of fixed arbor gang-ripping are 1) a decrease in the amount of primary yield; 2) an increase in the amount of salvage yield and work; 3) an increase in the importance of saw space sequencing; 4) an increase in the amount of salvage yield in long, thin pieces; and 5) a decrease in the total yield. Removing crook by an initial crosscut before gang-ripping (a procedure is described) will 1) result in yields that are mostly primary; 2) reduce the need for extensive salvage operations; 3) limit salvage to short, narrow pieces; and 4) make the saw space sequence unimportant. Crook amounts of 1/2 inch and greater should be removed. No. 1 Common lumber produces slightly more yield in the longest lengths (75 in.) than No. 2 Common lumber, but not enough to justify the 100 percent difference in price when the needs of the furniture and cabinet industries are considered.

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