Inch Bolt Torque Chart — Grade 2, 5 and 8 (UNC coarse)
Starting assembly torque for SAE J429 inch bolts, calculated from T = K × D × F with the clamp load F set at 75% of proof load. Dry uses K = 0.20; lubricated uses K = 0.15. Switch units below.
Not for structural A325 / A490 joints. Match dry or lubricated to the bolt as it is installed.
Torque (ft-lb)
| Size | Grade 2 dry | Grade 5 dry | Grade 8 dry | Grade 2 lubricated | Grade 5 lubricated | Grade 8 lubricated |
|---|---|---|---|---|---|---|
| 1/4-20 | 5.5 | 8.5 | 12 | 4.1 | 6.3 | 8.9 |
| 5/16-18 | 11 | 17 | 25 | 8.4 | 13 | 18 |
| 3/8-16 | 20 | 31 | 44 | 15 | 23 | 33 |
| 7/16-14 | 32 | 49 | 70 | 24 | 37 | 52 |
| 1/2-13 | 49 | 75 | 106 | 37 | 57 | 80 |
| 9/16-12 | 70 | 109 | 154 | 53 | 82 | 115 |
| 5/8-11 | 97 | 150 | 212 | 73 | 113 | 159 |
| 3/4-10 | 172 | 267 | 376 | 129 | 200 | 282 |
| 7/8-9 | 167 | 429 | 606 | 125 | 322 | 455 |
| 1-8 | 250 | 644 | 909 | 187 | 483 | 681 |
| 1-1/8-7 | 354 | 794 | 1,288 | 266 | 596 | 966 |
| 1-1/4-7 | 500 | 1,121 | 1,817 | 375 | 840 | 1,363 |
| 1-3/8-6 | 655 | 1,469 | 2,382 | 491 | 1,102 | 1,786 |
| 1-1/2-6 | 869 | 1,950 | 3,162 | 652 | 1,462 | 2,371 |
Grade 2 proof drops from 55 ksi to 33 ksi above 3/4 in, and Grade 5 from 85 ksi to 74 ksi above 1 in — that is why those columns step. SAE J429 covers sizes to 1-1/2 in. Grade 2 bolts 1/4–3/4 in longer than 6 in are supplied with Grade 1 properties.
Do not use these values for pretensioned or slip-critical structural joints (ASTM F3125 A325 / A490 under RCSC). Those are installed by turn-of-nut, calibrated wrench, twist-off or DTI methods.
Lubrication changes the answer. Applying a dry value to a lubricated, plated or anti-seized bolt can yield or break it. The manufacturer’s or engineer’s value always governs.
How to read this chart: find the size, pick the grade, then pick dry or lubricated to match the bolt as it will actually go in. Worked example — 1/2-13 Grade 5, dry: stress area 0.1419 in² × 85,000 psi proof = 12,062 lb proof load. Clamp at 75% = 9,046 lb. T = 0.20 × 0.500 in × 9,046 lb = 905 in-lb = 75 ft-lb (102 N·m). Oiled (K 0.15): 57 ft-lb.
Stress area, proof load and clamp load
| Size | Stress area (in²) | Grade 2 proof load (lb) | Grade 2 clamp, 75% (lb) | Grade 5 proof load (lb) | Grade 5 clamp, 75% (lb) | Grade 8 proof load (lb) | Grade 8 clamp, 75% (lb) |
|---|---|---|---|---|---|---|---|
| 1/4-20 | 0.0318 | 1,750 | 1,313 | 2,705 | 2,029 | 3,819 | 2,864 |
| 5/16-18 | 0.0524 | 2,884 | 2,163 | 4,457 | 3,342 | 6,292 | 4,719 |
| 3/8-16 | 0.0775 | 4,262 | 3,196 | 6,587 | 4,940 | 9,299 | 6,974 |
| 7/16-14 | 0.1063 | 5,847 | 4,385 | 9,036 | 6,777 | 12,757 | 9,568 |
| 1/2-13 | 0.1419 | 7,804 | 5,853 | 12,061 | 9,046 | 17,028 | 12,771 |
| 9/16-12 | 0.1819 | 10,007 | 7,505 | 15,465 | 11,599 | 21,833 | 16,375 |
| 5/8-11 | 0.2260 | 12,430 | 9,323 | 19,210 | 14,408 | 27,120 | 20,340 |
| 3/4-10 | 0.3345 | 18,395 | 13,797 | 28,429 | 21,322 | 40,135 | 30,101 |
| 7/8-9 | 0.4617 | 15,237 | 11,428 | 39,247 | 29,436 | 55,408 | 41,556 |
| 1-8 | 0.6057 | 19,990 | 14,992 | 51,488 | 38,616 | 72,689 | 54,517 |
| 1-1/8-7 | 0.7633 | 25,188 | 18,891 | 56,482 | 42,362 | 91,593 | 68,695 |
| 1-1/4-7 | 0.9691 | 31,981 | 23,986 | 71,714 | 53,786 | 116,293 | 87,220 |
| 1-3/8-6 | 1.1549 | 38,111 | 28,583 | 85,461 | 64,096 | 138,586 | 103,939 |
| 1-1/2-6 | 1.4053 | 46,373 | 34,780 | 103,989 | 77,991 | 168,630 | 126,473 |
K factor: the number that moves the answer
| Condition | Typical K | Note |
|---|---|---|
| Plain steel, dry, as received | 0.20 | This chart’s dry column |
| Zinc plated, dry | 0.17 – 0.22 | Varies with plating and topcoat; many sealers add lubricity |
| Light machine oil | 0.15 – 0.18 | This chart’s lubricated column uses 0.15 |
| Moly paste or anti-seize | 0.10 – 0.13 | Big drop — a dry value here can yield the bolt |
| Stainless on stainless, dry | 0.25 – 0.35 | Galling risk: use anti-seize and tighten slowly |
Typical ranges only. Actual K depends on finish, lubricant, washer, speed and even the batch — test critical joints.
Chart torque converts to actual preload with a scatter of about ±25–30%, because friction varies. Thread-forming and thread-cutting screws have no universal torque — test on the actual joint. Published hex-bolt values are not automatically valid for socket head cap screws.
