Date of Graduation

1990

Document Type

Dissertation/Thesis

Abstract

The custom millwork industry currently purchases about 89 percent of its hardwood lumber from the top NHLA grades, FAS and FAS1F (1F&Btr). For many millwork producers, the abundance of yellow-poplar in the Appalachian region, its cost and machining properties make it an attractive wood species. The price discrepancies between 1F&Btr yellow-poplar and lower grades are not necessarily justified by observed variation in cutting yield. To determine the effect of NHLA board grade on millwork cutting yields, a database was assembled, detailing information on the type, size and location of defects on the faces of 479 re-graded 4/4 kiln-dried yellow-poplar boards. The grades studied were 1F&Btr, No. 1 Common, No. 2A Common and No. 2B Common. OPTYLD (Giese and McDonald, 1982) is a computer program that simulates the sawing of a board into clear pieces in a way that maximizes surface area. A revised version of OPTYLD was used with five single primary rip widths of 1 to 5 inches to simulate the ripping, crosscutting and re-ripping of boards into random length Grade I, II and III cuttings, as established by the Architectural Woodwork Institute, based on the better face of the boards. Mean yield, mean cutting width and mean cutting length were found to be generally higher from costlier grades. Average yields from 1F&Btr, No. 1, No. 2A and No. 2B Common yellow-poplar were 85, 69, 70 and 70 percent, respectively. However, when the production of paint-grade cuttings was simulated, the average yields were 85, 82, 79 and 76 percent from the four grades. This suggests the substitution of Common grades for much yellow-poplar now purchased as 1F&Btr. Cutting lengths resulting from the sawing simulation were consistently and significantly shorter for each Common grade than they were for every higher grade studied. Cutting widths were also examined, but fewer significant differences were found. It is concluded that 1F&Btr is superior to the other grades when producing clear-finish cuttings. However, the use of the Common grades for paint-grade cuttings is clearly indicated. The results are applicable to other industries, including the dimension and furniture industries.

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