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TABLE 4. <br />Sheet Metal Screws: Plywood-to-Metal Connections(a) <br />Ultimate Lateral Load (lb)(b) <br />Plywood <br />Screw SizeFramingThickness 1/4"-20 Self <br />(in.) #8 #10 #12 #14 Tapping Screw <br />0.080"1/4 130 150 170 180 220 <br />Aluminum 1/2 350 470 500 520 500 <br />3/4 660 680 790 850* 790* <br />0.078" 1/4 130 150 170 180 220 <br />Galvanized 1/2 350 470 500 520 500 <br />Steel (14 gage) 3/4 660 680 800 900 850 <br />(a) Plywood was A-C EXT (all plies Group 1). <br />(b) Loads denoted by an asterisk(*) were limited by screw-to-framing strength; <br />others were limited by plywood strength. <br />3 <br />correction factors presented in Table 5. <br />Correction factors apply for both <br />lateral and withdrawal loading. The <br />adjustment factor for the highest <br />numbered species group present in <br />any veneer should be used. <br />Fastening Into Plywood Panel Edges <br />Fastening into plywood panel edges is <br />not normally recommended. For some <br />purposes, however, edge fastening <br />may be necessary. Table 6 presents <br />ultimate lateral and withdrawal loads <br />for various sizes of wood screws in <br />this application. <br />Estimating Allowable <br />Design Loads <br />It is the responsibility of the designer <br />to select a working load suitable for <br />the particular application. A high <br />degree of variability is inherent in <br />individual fastener test results. <br />Therefore, for screws in withdrawal, a <br />working load of about one-sixth of the <br />ultimate load has traditionally been <br />used for long-duration loads. For <br />normal load duration, the long-term <br />working load may be increased by <br />10 percent. Normal load duration <br />contemplates fully stressing the con- <br />nection for approximately ten years, <br />either continuously or cumulatively. <br />TABLE 3. <br />Wood and Sheet Metal Screws: Metal-to-Plywood Connections(a) <br />Depth of Average Ultimate Withdrawal Load (lb) <br />Threaded <br />Penetration Screw Size <br />(in.)#6 #8 #10 #12 #14 #16 <br />3/8 150 180 205 – – – <br />1/2 200 240 275 315 350 – <br />5/8 250 295 345 390 440 – <br />3/4 300 355 415 470 525 – <br />1 – – – 625 700 775 <br />1-1/8 – – – 705 790 875 <br />2-1/4 – – – –1580 – <br />(a) Plywood was C-D grade with exterior glue (all plies Group 1). <br />0.25" <br />Wood Screw Sheet Metal Screw <br />TN,E830.0 4/13/00 10:11 AM Page 3 <br />Page 31 <br />© 1995 APA - The Engineered Wood Association <br />2130 N Grand Ave <br />10/1/2024