Technical Data Suggested Tightening Torque1 Values To Produce Corresponding Bolt Clamping Loads SAE Grade 2 Bolts Size Proof Load D (in.) A (sq. in.) (min psi) (psi) 74,000 55,000 Clamp2 Tightening Torque Tensile Load Dry Lub. Strength P (lb.) K=0.20 K=0.15 240 280 380 420 580 lb. in. lb. in. 5 4 6 5 10 8 12 9 19 14 4-40 4-48 6-32 6-40 8-32 0.1120 0.1120 0.1380 0.1380 0.1640 0.00604 0.00661 0.00909 0.01015 0.01400 8-36 10-24 10-32 1/4-20 1/4-28 0.1640 0.1900 0.1900 0.2500 0.2500 0.01474 0.01750 0.02000 0.0318 0.0364 600 720 820 1320 1500 5/16-18 5/16-24 3/8-16 3/8-24 7/16-14 0.3125 0.3125 0.3750 0.3750 0.4375 0.0524 0.0580 0.0775 0.0878 0.1063 7/16-20 1/2-13 1/2-20 9/16-12 9/16-18 0.4375 0.5000 0.5000 0.5625 0.5625 5/8-11 5/8-18 3/4-10 3/4-16 7/8-9 Proof Load (min psi) 120,000 (psi) 85,000 Clamp2 Tightening Torque Load Dry Lub. P (lb.) K=0.20 K=0.15 380 420 580 640 900 lb. in. lb. in. 8 6 9 7 16 12 18 13 30 22 15 21 23 49 56 lb. ft. 8 9 15 17 24 940 1120 1285 2020 2320 2160 2400 3200 3620 4380 20 27 31 66 76 lb. ft. 11 12 20 23 30 0.1187 0.1419 0.1599 0.1820 0.2030 4900 5840 6600 7500 8400 35 50 55 70 80 0.6250 0.6250 0.7500 0.7500 0.8750 0.2260 0.2560 0.3340 0.3730 0.4620 9300 10600 13800 15400 11400 7/8-14 1-8 1-12 1-1/8-7 1-1/8-12 0.8750 1.0000 1.0000 1.1250 1.1250 0.5090 0.6060 0.6630 0.7630 0.8560 1-1/4-7 1-1/4-12 1-3/8-6 1-3/8-12 1-1/2-6 1.2500 1.2500 1.3750 1.3750 1.5000 1-1/2-12 1.5000 P (lb.) K=0.20 K=0.15 P (lb.) K=0.20 K=0.15 480 520 720 800 1100 lb. in. lb. in. 11 8 12 9 20 15 22 17 36 27 540 600 820 920 1260 lb. in. lb. in. 12 9 13 10 23 17 25 19 41 31 1160 1380 1580 2500 2860 3340 3700 4940 5600 6800 23 32 36 75 86 lb. ft. 13 14 23 25 35 25 35 40 55 60 7550 9050 10700 11600 12950 55 75 90 110 120 100 110 175 195 165 75 85 130 145 125 14400 16300 21300 23800 29400 12600 15000 16400 18900 21200 185 250 270 350 400 140 190 200 270 300 0.9690 1.0730 1.1550 1.3150 1.4050 24000 26600 28600 32500 34800 500 550 660 740 870 1.5800 39100 980 33,000 29 39 45 96 108 lb. ft. 16 18 30 45 45 1320 1580 1800 2860 3280 4120 4560 6100 6900 8400 38 52 60 120 144 lb. ft. 21 24 40 45 60 40 55 65 80 90 9350 11200 12600 14350 16000 70 95 100 135 150 150 170 260 300 430 110 130 200 220 320 17800 20150 26300 29400 36400 32400 38600 42200 42300 47500 470 640 700 800 880 350 480 530 600 660 380 420 490 560 650 53800 59600 64100 73000 78000 1120 1240 1460 1680 1940 730 87700 2200 1. Tightening torque values are calculated from the formula T = KDP, where T = tightening torque, lb-in.; K = torque-friction coefficient; D = nominal bolt diameter, in.; and P = bolt clamping load developed by tightening. lb. 2. Clamp load is also known as preload or initial load in tension on bolt. Clamp load (lb.) is calculated by arbitrarily assuming usable bolt strength is 75% of bolt proof load (psi) times tensile stress area (sq. in.) of threaded section of each bolt size. Higher or lower values of clamp load can be used depending on the application requirements and the judgement of the designer. 3. Tensile strength (min psi) of all Grade 7 bolts is 133,000. Proof load is 105,000 psi. 4. Tensile strength (min psi) of all Grade 8 bolts is 150,000 psi. Proof load is 120,000 psi. Ref.: Fastening Reference. Machine Design. Nov. 1977. Bolt Clamping Force vs. Tightening Torque for Unlubricated Steel Bolts. 105,000 74,000 4720 5220 7000 7900 9550 43 60 68 144 168 lb. ft. 25 25 45 50 70 32 45 51 108 120 lb. ft. 18 20 35 35 55 50 70 80 100 110 10700 12750 14400 16400 18250 80 110 120 150 170 60 80 90 110 130 190 210 320 360 520 140 160 240 280 400 20350 23000 30100 33600 41600 220 240 380 420 600 170 180 280 320 460 40100 47700 52200 60100 67400 580 800 860 1120 1260 440 600 660 840 940 45800 54500 59700 68700 77000 660 900 1000 1280 1440 500 680 740 960 1080 840 920 1100 1260 1460 76300 84500 91000 104000 111000 1580 1760 2080 2380 2780 1100 1320 1560 1780 2080 87200 96600 104000 118400 126500 1820 2000 2380 2720 3160 1360 1500 1780 2040 2360 1640 124005 3100 2320 142200 3560 2660 10,000 9,000 5/8"-11 8,000 1/2"- 13 7,000 3/4"-10 6,000 3/8"-16 5,000 4,000 5/16" -18 CATALOG 13 60,000 SAE Grade 84 Clamp2 Tightening Torque Clamp2 Tightening Torque Load Dry Lub. Load Dry Lub. 31 43 49 96 120 lb. ft. 17 19 30 35 50 Notes: 3,000 2,000 1,000 0 0 D48 SAE Grade 73 SAE Grade 5 Bolts Bolt Clamping Force (lbs.) D Bolt Dia. Tensile Stress Tensile Area Strength 100 200 300 400 500 600 700 Tightening Torque (inch-lbs.) 800 900 1000