Inch Fine Thread Torque Chart — Grade 2, 5 and 8 (UNF)
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 |
|---|---|---|---|---|---|---|
| 1/4-28 | 6.3 | 9.7 | 14 | 4.7 | 7.2 | 10 |
| 5/16-24 | 12 | 19 | 27 | 9.4 | 14 | 20 |
| 3/8-24 | 23 | 35 | 49 | 17 | 26 | 37 |
| 7/16-20 | 36 | 55 | 78 | 27 | 41 | 58 |
| 1/2-20 | 55 | 85 | 120 | 41 | 64 | 90 |
| 9/16-18 | 78 | 121 | 171 | 59 | 91 | 128 |
| 5/8-18 | 110 | 170 | 240 | 82 | 127 | 180 |
| 3/4-16 | 192 | 297 | 420 | 144 | 223 | 315 |
| 7/8-14 | 184 | 474 | 669 | 138 | 355 | 502 |
| 1-12 | 274 | 704 | 995 | 205 | 528 | 746 |
| 1-1/8-12 | 397 | 890 | 1,444 | 298 | 668 | 1,083 |
| 1-1/4-12 | 553 | 1,241 | 2,012 | 415 | 930 | 1,509 |
| 1-3/8-12 | 746 | 1,672 | 2,712 | 559 | 1,254 | 2,034 |
| 1-1/2-12 | 978 | 2,194 | 3,557 | 734 | 1,645 | 2,668 |
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) |
|---|---|---|---|---|---|---|---|
| 1/4-28 | 0.0364 | 2,001 | 1,500 | 3,092 | 2,319 | 4,365 | 3,274 |
| 5/16-24 | 0.0581 | 3,194 | 2,395 | 4,936 | 3,702 | 6,968 | 5,226 |
| 3/8-24 | 0.0878 | 4,831 | 3,623 | 7,465 | 5,599 | 10,539 | 7,905 |
| 7/16-20 | 0.1187 | 6,529 | 4,897 | 10,091 | 7,568 | 14,246 | 10,684 |
| 1/2-20 | 0.1600 | 8,797 | 6,598 | 13,596 | 10,197 | 19,194 | 14,396 |
| 9/16-18 | 0.2030 | 11,164 | 8,373 | 17,253 | 12,940 | 24,358 | 18,268 |
| 5/8-18 | 0.2560 | 14,078 | 10,558 | 21,756 | 16,317 | 30,715 | 23,036 |
| 3/4-16 | 0.3730 | 20,513 | 15,385 | 31,702 | 23,776 | 44,755 | 33,566 |
| 7/8-14 | 0.5095 | 16,813 | 12,609 | 43,305 | 32,479 | 61,137 | 45,853 |
| 1-12 | 0.6630 | 21,880 | 16,410 | 56,359 | 42,269 | 79,565 | 59,674 |
| 1-1/8-12 | 0.8557 | 28,239 | 21,179 | 63,323 | 47,493 | 102,687 | 77,015 |
| 1-1/4-12 | 1.0729 | 35,407 | 26,555 | 79,398 | 59,548 | 128,753 | 96,565 |
| 1-3/8-12 | 1.3147 | 43,386 | 32,539 | 97,289 | 72,967 | 157,765 | 118,324 |
| 1-1/2-12 | 1.5810 | 52,174 | 39,130 | 116,996 | 87,747 | 189,723 | 142,292 |
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.
