Screw-holding Capacity of Two Furniture-grade Plywoods

niture-grade plywood. The information is greatly needed for manufacturing, buyUltimate screw withdrawal loads (USWLs) from panel face and edge of furnitureing and selling plywood panels, and for grade southern pine (Pinus spp.) and sweetgum (Liquidambar styraeiflua L.) plywood better construction of ]plywood joints in were evaluated at five moisture contents (MCs). Both face and edge USWL decreased furniture and cabinets. in general with increases in MC within the hygroscopic range. The effect of moisture on The purpose of this study was to measedgeUSWLwasmorepronouncedthanonfaceUSWL.Foreachplywood, USWLfrom and quantify the influence of moisthe panel face was significantly larger than the USWL value from the panel edge. At ure higher MC levels, edge screw-holding capacities deteriorated more rapidly than face ture, fastening direction, and wood species on USWL of interior-type plywood screw-holding capacities. For plywood with comparable properties (e.g., panel thickmanufactured for fumiture, cabinet, and ness, bending stiffness and strength), wood species (pine vs. sweetgum) had an millworkmarkets. insignificant effect on USWL. Thus, sweetgum plywood is as good as pine plywood in MATERIALS AND METHODS screw-holding strength. Interior-type southern pine (Pinus spp.) and sweetgum (Liquidambar styraciflua L.) plywood panels were used in the study. Six 4by 4-foot (1.22by 1.22-m) Interior-type plywoodis widely used ducted in both dry and soaked conditions panels of each type of plywood were in construction of furniture and cabinets, for wood-based panels. However, for inobtained from a plywood manufacturer The integrity of such construction is freterior-type plywood used for furniture in the south. The panels had a 5-ply conquently dependent upon the connections and cabinet manufacturing, plywood struction with a panel thickness of 23/32 between its components. For maximum joints or constructions at complete waterinch (18 ram). The product was develstrength and stability, each connection soaked condition are rare. On the other oped for the furniture and cabinet indusrequires a design that is adapted to the hand, MC of the panel does fluctuate try in the south. fastener type and to the strength properwithin the hygroscopic mangedepending Five 19by 3by 23/32-inch (483by ties of the individual structural members. 1 on geographic location, season of the 76by 18-ram) specimens along both Ultimate fastener withdrawal loads for year, etc. This fluctuation in MC can sigmaterial directions from each of the panplywood joints depend on fastener type nificantly alter the screw-holding capacels were cut for bending modulus of elas(screw or nail), fastening direction (face ity of the panel and its structural integrity, ticity (MOE) and modulus of rupture or edge), panel moisture content (MC), Very little information exists, however, (MOR) tests according to the ASTM and wood species used to manufacture on the effects of moisture, fastening distandard, 2 giving a total of 30 specimens the plywood. The ASTM standard 2specirection, and wood species on the ultimate for each type of plywood. Specimens ties that screw withdrawal tests be conscrew withdrawal load (USWL) for furwere conditioned at 25°C and 55 percent The author is an Assistant Professor, Louisiana Forest Prod. Lab., School of Forestry, IAnonymous. 1995.Fastenerloadsfor plywood Wildlife, and Fisheries, Louisiana State Univ. Agri. Center, Baton Rouge, LA 70803. The screws. APATech. NoteNo.ES30C. APA,Tacoma, authorwishes to thankRoy O. Martin Lumber Co., LeMoyen, LA, for providing the plywood Wash. 4 pp. and funding for the study. This paper (No. 98-22-0213) is published with the approval of the 2AmericanSociety for Testing andMaterials. 1996. Directorof the Louisiana Agri. Expt. Sta. Thispaper wasreceived for publication inJuly 1998. Standard methods for evaluating properties of Reprint No. 8847. wood-based fiber and particle panel materials. J"Forest Products Society Member. ASTM D 1037-96. West Conshohocken, Pa. pp. ©Forest Products Society 1999. 137-166. Forest Prod.J.49(4):56-59.