Grade 5 & Grade 8 Tightening Torque Guide
USS GRADE 5
Coarse Thread
| Size | Clamp Load | Plain | Plated |
|---|---|---|---|
| 1/4-20 ( .250 ) | 2,025 | 8 ft-lb | 76 in-lb |
| 5/16-18 ( .3125) | 3,338 | 17 ft-lb | 13 ft-lb |
| 3/8-16 ( .375 ) | 4,950 | 31 ft-lb | 23 ft-lb |
| 7/16-14 ( .4375) | 6,788 | 50 ft-lb | 37 ft-lb |
| 1/2-13 ( .500 ) | 9,075 | 76 ft-lb | 57 ft-lb |
| 9/16-12 ( .5625) | 11,625 | 109 ft-lb | 82 ft-lb |
| 5/8-11 ( .625 ) | 14,400 | 150 ft-lb | 112 ft-lb |
| 3/4-10 ( .750 ) | 21,300 | 266 ft-lb | 200 ft-lb |
| 7/8-9 ( .875 ) | 29,475 | 430 ft-lb | 322 ft-lb |
| 1-8 (1.000 ) | 38,625 | 644 ft-lb | 483 ft-lb |
SAE GRADE 5
Fine Thread
| Size | Clamp Load | Plain | Plated |
|---|---|---|---|
| 1/4-28 ( .250 ) | 2,325 | 10 ft-lb | 87 in-lb |
| 5/16-24 ( .3125) | 3,675 | 19 ft-lb | 14 ft-lb |
| 3/8-24 ( .375 ) | 5,588 | 35 ft-lb | 26 ft-lb |
| 7/16-20 ( .4375) | 7,575 | 55 ft-lb | 41 ft-lb |
| 1/2-20 ( .500 ) | 10,200 | 85 ft-lb | 64 ft-lb |
| 9/16-18 ( .5625) | 12,975 | 122 ft-lb | 91 ft-lb |
| 5/8-18 ( .625 ) | 16,350 | 170 ft-lb | 128 ft-lb |
| 3/4-16 ( .750 ) | 23,775 | 297 ft-lb | 223 ft-lb |
| 7/8-14 ( .875 ) | 32,475 | 474 ft-lb | 355 ft-lb |
| 1-12 (1.000 ) | 42,300 | 705 ft-lb | 529 ft-lb |
USS GRADE 8
Coarse Thread
| Size | Clamp Load | Plain | Plated |
|---|---|---|---|
| 1/4-20 ( .250 ) | 2,850 | 12 ft-lb | 9 ft-lb |
| 5/16-18 ( .3125) | 4,725 | 25 ft-lb | 18 ft-lb |
| 3/8-16 ( .375 ) | 6,975 | 44 ft-lb | 33 ft-lb |
| 7/16-14 ( .4375) | 9,600 | 70 ft-lb | 52 ft-lb |
| 1/2-13 ( .500 ) | 12,750 | 106 ft-lb | 80 ft-lb |
| 9/16-12 ( .5625) | 16,350 | 153 ft-lb | 115 ft-lb |
| 5/8-11 ( .625 ) | 20,325 | 212 ft-lb | 159 ft-lb |
| 3/4-10 ( .750 ) | 30,075 | 376 ft-lb | 282 ft-lb |
| 7/8-9 ( .875 ) | 41,550 | 606 ft-lb | 454 ft-lb |
| 1-8 (1.000 ) | 54,525 | 909 ft-lb | 682 ft-lb |
SAE GRADE 8
Fine Thread
| Size | Clamp Load | Plain | Plated |
|---|---|---|---|
| 1/4-28 ( .250 ) | 3,263 | 14 ft-lb | 10 ft-lb |
| 5/16-24 ( .3125) | 5,113 | 27 ft-lb | 20 ft-lb |
| 3/8-24 ( .375 ) | 7,875 | 49 ft-lb | 37 ft-lb |
| 7/16-20 ( .4375) | 10,650 | 78 ft-lb | 58 ft-lb |
| 1/2-20 ( .500 ) | 14,400 | 120 ft-lb | 90 ft-lb |
| 9/16-18 ( .5625) | 18,300 | 172 ft-lb | 129 ft-lb |
| 5/8-18 ( .625 ) | 23,025 | 240 ft-lb | 180 ft-lb |
| 3/4-16 ( .750 ) | 33,600 | 420 ft-lb | 315 ft-lb |
| 7/8-14 ( .875 ) | 45,825 | 668 ft-lb | 501 ft-lb |
| 1-12 (1.000 ) | 59,700 | 995 ft-lb | 746 ft-lb |
TIGHTENING TORQUE GUIDE based on IFI 5th Edition Technical Data N-12/N-16, using Equation (1) and a torque coefficient, K-0.20 for non-plated steel fasteners and K-0.15 for plated fasteners. These figures represent an estimate of torque (torque being the measurement of friction, not tension) required to induce a given preload (clamp load) in a bolt for non-critical applications only. For critical or special applications where greater control is desired, this should be experimentally determined. This applies to washer faced or double chamfered hex nuts (or bolts, if bolt is torqued) having a width across flats of approximately 1.5 times the nominal diameter and having threads free of interference.
Because of the many interrelated variables that directly or indirectly affect friction, such as surface texture, type of coating or finish, lubrication, speed of tightening, human error, etc., it is possible to experience as much as ±25% deviation in preload (clamp load) with the use of a torque wrench.