Safety User guide

General Bolt Tightening Torque
Thread
Tensile Stress
Area
SAE Grade 2 SAE Grade 5 SAE Grade 8
Size Tsa
75% Yield Strength (PSI) - 43000 75% Yield Strength (PSI) - 69000 75% Yield Strength (PSI) = 98000
Plain Zinc Plated Plain Zinc Plated Plain Zinc Plated
Square Inches Ft.Lb. Ft.Lb. Ft.Lb. Ft.Lb. Ft.Lb. Ft.Lb.
1/4-20. 0.0318 6 6 9 10 13 14
1/4-28. 0.0364 7 7 10 12 15 16
5/16-18. 0.0524 12 13 19 21 27 29
5/16-24. 0.0580 13 14 21 23 30 33
3/8-16. 0.0775 21 23 33 37 47 52
3/8-24. 0.0878 24 26 38 42 54 59
7/16-14. 0.1063 33 37 53 59 76 83
7/16-24. 0.1187 37 41 60 66 85 93
1/2-13. 0.1419 51 56 82 90 116 127
1/2-20. 0.1599 57 63 92 101 131 144
9/16-12. 0.1820 73 81 118 129 167 184
9/16-18. 0.2030 82 90 131 144 186 205
5/8-11. 0.2260 101 111 162 179 231 254
5/8-14. 0.2560 115 126 184 202 261 287
3/4-10. 0.3340 180 197 288 317 409 450
3/4-16. 0.3730 200 221 322 354 457 503
The reason all applications should be evaluated to determine the optimum tightening torque is that the K
factor in this formula is always an estimate.
The most commonly used bolting K factors arc 0.20 for plain finished bolts, 0.22 for zinc plated bolts,
and 0.10 for waxed or highly lubricated bolts
Formula: T= K x D x P
• T Target tighten torque (the result of this formula is in inch pounds, dividing by 12 yields foot pounds
• K Coefficient of friction (nut factor), always an estimation in this formula
• D Bolts nominal diameter in inches
• P Bolt's desired tensile load in pounds (generally 75% of yield strength) - [ P(lbs) = (75%) Yield
Strength * T
ensile Stress Area ]
Bolt Torque
10