Budynas-Nisbett:Shigley's lll.Design of Mechanical 8.Screws,Fasteners,and T©The McGraw-Hill 401 Mechanical Engineering Elements the Design of Companies,2008 Design,Eighth Edition Nonpermanent Joints 398 Mechanical Engineering Design Table 8-1 Nominal Coarse-Pitch Series Fine-Pitch Series Diameters and Areas of Major Tensile- Minor- Tensile- Minor- Coarse-Pitch and Fine Diameter Pitch Stress Diameter Pitch Stress Diameter d Area Ar Area Ar p Area A Area Ar Pitch Metric Threads.* mm mm mm2 mm2 mm mm2 mm2 1.6 0.35 1.27 1.07 2 0.40 2.07 1.79 2.5 0.45 3.39 2.98 0.5 5.03 4.47 3.5 0.6 6.78 6.00 4 0.7 8.78 7.75 0.8 14.2 12.7 6 20.1 17.9 8 1.25 36.6 32.8 1 39.2 36.0 10 1.5 58.0 52.3 1.25 61.2 56.3 12 1.75 84.3 76.3 1.25 92.1 86.0 14 2 115 104 1.5 125 116 16 2 157 144 1.5 167 157 20 2.5 245 225 1.5 272 259 24 3 353 324 2 384 365 30 3.5 561 519 2 621 596 36 817 759 2 915 884 42 4.5 1120 1050 2 1260 1230 48 1470 1380 2 1670 1630 56 5.5 2030 1910 2 2300 2250 64 2680 2520 2 3030 2980 72 3460 3280 2 3860 3800 80 6 4340 4140 1.5 4850 4800 90 6 5590 5360 2 6100 6020 100 6990 6740 2 7560 7470 110 2 9180 9080 *Theidat used o evthis table hve beobdfromANSIB1.1-1974B18.3.1-1978.Themino diameter was found from the equation d,=d-1.226 869p,and the pitch diameter fromd=d-0.649 519p.The mean of the pith diameter and the minor diameter was used to compute the tensilestressara Square and Acme threads,shown in Fig.8-3a and b,respectively,are used on screws when power is to be transmitted.Table 8-3 lists the preferred pitches for inch- series Acme threads.However,other pitches can be and often are used,since the need for a standard for such threads is not great. Modifications are frequently made to both Acme and square threads.For instance, the square thread is sometimes modified by cutting the space between the teeth so as to have an included thread angle of 10 to 15.This is not difficult,since these threads are usually cut with a single-point tool anyhow;the modification retains most of the high efficiency inherent in square threads and makes the cutting simpler.Acme threadsBudynas−Nisbett: Shigley’s Mechanical Engineering Design, Eighth Edition III. Design of Mechanical Elements 8. Screws, Fasteners, and the Design of Nonpermanent Joints © The McGraw−Hill 401 Companies, 2008 398 Mechanical Engineering Design Nominal Coarse-Pitch Series Fine-Pitch Series Major Tensile- Minor- Tensile- Minor￾Diameter Pitch Stress Diameter Pitch Stress Diameter d p Area At Area Ar p Area At Area Ar mm mm mm2 mm2 mm mm2 mm2 1.6 0.35 1.27 1.07 2 0.40 2.07 1.79 2.5 0.45 3.39 2.98 3 0.5 5.03 4.47 3.5 0.6 6.78 6.00 4 0.7 8.78 7.75 5 0.8 14.2 12.7 6 1 20.1 17.9 8 1.25 36.6 32.8 1 39.2 36.0 10 1.5 58.0 52.3 1.25 61.2 56.3 12 1.75 84.3 76.3 1.25 92.1 86.0 14 2 115 104 1.5 125 116 16 2 157 144 1.5 167 157 20 2.5 245 225 1.5 272 259 24 3 353 324 2 384 365 30 3.5 561 519 2 621 596 36 4 817 759 2 915 884 42 4.5 1120 1050 2 1260 1230 48 5 1470 1380 2 1670 1630 56 5.5 2030 1910 2 2300 2250 64 6 2680 2520 2 3030 2980 72 6 3460 3280 2 3860 3800 80 6 4340 4140 1.5 4850 4800 90 6 5590 5360 2 6100 6020 100 6 6990 6740 2 7560 7470 110 2 9180 9080 *The equations and data used to develop this table have been obtained from ANSI B1.1-1974 and B18.3.1-1978. The minor diameter was found from the equation dr d 1.226 869p, and the pitch diameter from dp d 0.649 519p. The mean of the pitch diameter and the minor diameter was used to compute the tensile-stress area. Table 8–1 Diameters and Areas of Coarse-Pitch and Fine￾Pitch Metric Threads.* Square and Acme threads, shown in Fig. 8–3a and b, respectively, are used on screws when power is to be transmitted. Table 8–3 lists the preferred pitches for inch￾series Acme threads. However, other pitches can be and often are used, since the need for a standard for such threads is not great. Modifications are frequently made to both Acme and square threads. For instance, the square thread is sometimes modified by cutting the space between the teeth so as to have an included thread angle of 10 to 15◦. This is not difficult, since these threads are usually cut with a single-point tool anyhow; the modification retains most of the high efficiency inherent in square threads and makes the cutting simpler. Acme threads