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Bolt Torque Chart

Recommended assembly torque for SAE Grade 2/5/8, ISO 8.8/10.9/12.9, and stainless A2-70 fasteners — dry and lubricated.

True Precision Machining
Section view of a bolted joint: a socket-head cap screw clamping two plates, with applied torque T at the head, clamp force F through the joint, and friction losses under the head and in the threads. The formula T equals K times D times F is shown with friction factor K of 0.20 dry and 0.15 oiled, and a bar showing that roughly 90 percent of applied torque is lost to friction, leaving only about 10 percent as bolt stretch and clamp force. T (TORQUE) CLAMP FORCE F CLAMP FORCE F ~90% LOST TO FRICTION D (NOM Ø) BOLTED JOINT — SECTION Torque is a proxy — what the joint actually needs is clamp force F. T = K · D · F TORQUE (IN-LB) = FRICTION FACTOR × NOMINAL Ø (IN) × PRELOAD (LBF) K = FRICTION FACTOR: DRY 0.20 · OILED 0.15 ~90% LOST TO FRICTION (TYPICAL) UNDER-HEAD ~50% THREADS ~40% CLAMP (STRETCH) ~10% WHERE THE TORQUE GOES Friction eats ~90% of the torque — which is why lubrication changes the number.
Size Aₜ in² Recommended assembly torque — ft-lb @ 75% yield preload
SAE Grade 2 57 ksi yield SAE Grade 5 92 ksi yield SAE Grade 8 130 ksi yield ISO 12.9 160 ksi yield A2-70 SS 65 ksi yield
Dry Oiled Dry Oiled Dry Oiled Dry Oiled Dry Oiled
Inch — Unified coarse (UNC)
1/4-20 0.0318 5.7 4.2 9.1 6.9 13 9.7 16 12 6.5 4.8
5/16-18 0.0524 12 8.8 19 14 27 20 33 25 13 10.0
3/8-16 0.0775 21 16 33 25 47 35 58 44 24 18
7/16-14 0.1063 33 25 53 40 76 57 93 70 38 28
1/2-13 0.1419 51 38 82 61 115 86 142 106 58 43
9/16-12 0.1820 73 55 118 88 166 125 205 154 83 62
5/8-11 0.2260 101 75 162 122 230 172 283 212 115 86
3/4-10 0.3340 178 134 288 216 407 305 501 376 204 153
7/8-9 0.4620 182 136 465 349 657 493 809 606 328 246
1-8 0.6060 273 205 697 523 985 739 1,212 909 492 369
Metric — ISO coarse
M5 0.0220 3.1 2.3 5.0 3.7 7.0 5.3 8.7 6.5 3.5 2.6
M6 0.0312 5.3 3.9 8.5 6.4 12 9.0 15 11 6.0 4.5
M8 0.0568 13 9.6 21 15 29 22 36 27 15 11
M10 0.0900 25 19 41 31 58 43 71 53 29 22
M12 0.1310 44 33 71 53 101 75 124 93 50 38
M16 0.2430 109 82 176 132 249 187 306 230 124 93
M20 0.3800 135 101 344 258 486 365 598 449 243 182

Key: all values in ft-lb at 75% of yield preload. Dry = uncoated steel-on-steel, K = 0.20. Oiled = light oil / wax, K = 0.15. Aₜ = thread tensile stress area (in²).

T = K × D × F, where F = 0.75 × yield × tensile area. SAE Grade 5 = ISO 8.8 (92 ksi); SAE Grade 8 = ISO 10.9 (130 ksi). A2-70 = 304 stainless. Per SAE J429, Grade 2 yield drops to 36 ksi over 3/4″ dia — the 7/8-9 and 1-8 rows use 36 ksi.

Reduce torque 30–50% in tapped holes of soft material (aluminum, plastics) to protect the threads. For lubrication factors not shown (zinc K = 0.18, anti-seize K = 0.12, PTFE K = 0.09) and any size, grade, or preload combination, use the interactive bolt torque calculator.

Free engineering reference from True Precision Machining
trueprecisionmachining.com · 805-964-4545 · Buellton, CA · AS9100 / ISO 9001 / ITAR
Torque at 75% of yield preload, T = K·D·F — verify against OEM specs for critical joints. · September 2026