Metric bolts
Metric coarse - tightening torque in Nm (friction μ = 0.14)
| Thread | Pitch | 4.6 | 5.8 | 8.8 | 10.9 | 12.9 | Preload 8.8 kN | Preload 10.9 kN |
|---|
| M3 | 0.5 | 0.5 | 0.9 | 1.4 | 2.1 | 2.5 | 2.5 | 3.6 |
| M4 | 0.7 | 1.2 | 2.2 | 3.3 | 4.8 | 5.6 | 4.3 | 6.3 |
| M5 | 0.8 | 2.4 | 4.3 | 6.5 | 9.5 | 11.1 | 7 | 10.3 |
| M6 | 1 | 4 | 7 | 11 | 17 | 19 | 9.9 | 14.6 |
| M8 | 1.25 | 10 | 18 | 27 | 40 | 47 | 18.1 | 26.6 |
| M10 | 1.5 | 20 | 35 | 54 | 79 | 93 | 28.8 | 42.3 |
| M12 | 1.75 | 35 | 61 | 93 | 137 | 160 | 42 | 61.7 |
| M14 | 2 | 56 | 98 | 149 | 218 | 256 | 57.6 | 84.6 |
| M16 | 2 | 86 | 151 | 230 | 338 | 395 | 78.9 | 115.9 |
| M18 | 2.5 | 120 | 209 | 329 | 469 | 549 | 99.3 | 141.4 |
| M20 | 2.5 | 169 | 295 | 464 | 661 | 773 | 127.2 | 181.1 |
| M22 | 2.5 | 231 | 404 | 635 | 904 | 1058 | 158.5 | 225.8 |
| M24 | 3 | 290 | 508 | 798 | 1136 | 1330 | 183.1 | 260.8 |
| M27 | 3 | 428 | 749 | 1176 | 1675 | 1960 | 240.3 | 342.3 |
| M30 | 3.5 | 581 | 1017 | 1598 | 2275 | 2663 | 292.5 | 416.5 |
| M33 | 3.5 | 786 | 1376 | 2162 | 3079 | 3604 | 363.7 | 518 |
| M36 | 4 | 1011 | 1769 | 2780 | 3959 | 4633 | 427.3 | 608.5 |
Torques are calculated to VDI 2230 for 90% use of the bolt's minimum yield strength, with thread and head friction μ = 0.14 (zinc-plated or lightly oiled), standard hex heads and medium clearance holes. 1 Nm = 0.738 ft-lb.
Metric fine - Nm (μ = 0.14)
| Thread | 8.8 | 10.9 | 12.9 |
|---|
| M8 × 1 | 29 | 43 | 50 |
| M10 × 1.25 | 57 | 83 | 98 |
| M10 × 1 | 60 | 88 | 103 |
| M12 × 1.5 | 97 | 143 | 167 |
| M12 × 1.25 | 101 | 149 | 174 |
| M14 × 1.5 | 160 | 235 | 275 |
| M16 × 1.5 | 245 | 359 | 421 |
| M18 × 1.5 | 368 | 524 | 613 |
| M20 × 1.5 | 512 | 729 | 853 |
| M22 × 1.5 | 693 | 986 | 1154 |
| M24 × 2 | 866 | 1233 | 1443 |
| M27 × 2 | 1263 | 1799 | 2105 |
| M30 × 2 | 1758 | 2504 | 2931 |
Stainless steel - Nm (lubricated, μ = 0.14)
| Thread | A2-70 / A4-70 | A4-80 |
|---|
| M3 | 1 | 1.3 |
| M4 | 2.3 | 3.1 |
| M5 | 4.6 | 6.1 |
| M6 | 8 | 11 |
| M8 | 19 | 26 |
| M10 | 38 | 51 |
| M12 | 65 | 87 |
| M14 | 105 | 139 |
| M16 | 162 | 216 |
| M18 | 224 | 299 |
| M20 | 316 | 422 |
| M22 | 433 | 577 |
| M24 | 544 | 725 |
Inch bolts and adjustments
SAE Grade 5 and 8 - UNC (μ = 0.14)
| UNC | Gr 5 ft-lb | Gr 8 ft-lb | Gr 5 Nm | Gr 8 Nm |
|---|
| 1/4"-20 | 10 | 13 | 13 | 18 |
| 5/16"-18 | 19 | 27 | 26 | 36 |
| 3/8"-16 | 33 | 46 | 44 | 63 |
| 7/16"-14 | 52 | 73 | 70 | 99 |
| 1/2"-13 | 79 | 112 | 108 | 152 |
| 9/16"-12 | 113 | 160 | 153 | 216 |
| 5/8"-11 | 157 | 222 | 213 | 301 |
| 3/4"-10 | 278 | 392 | 376 | 532 |
| 7/8"-9 | 446 | 630 | 604 | 854 |
| 1"-8 | 667 | 942 | 904 | 1278 |
SAE Grade 5 and 8 - UNF (μ = 0.14)
| UNF | Gr 5 ft-lb | Gr 8 ft-lb | Gr 5 Nm | Gr 8 Nm |
|---|
| 1/4"-28 | 11 | 15 | 15 | 21 |
| 5/16"-24 | 21 | 30 | 28 | 40 |
| 3/8"-24 | 37 | 52 | 50 | 71 |
| 7/16"-20 | 57 | 81 | 78 | 110 |
| 1/2"-20 | 89 | 125 | 120 | 170 |
| 9/16"-18 | 125 | 177 | 169 | 239 |
| 5/8"-18 | 176 | 249 | 239 | 337 |
| 3/4"-16 | 307 | 433 | 416 | 587 |
| 7/8"-14 | 487 | 688 | 660 | 933 |
| 1"-12 | 724 | 1023 | 981 | 1386 |
Adjusting for lubrication (to reach the same preload)
| Condition of threads | Typical μ | Multiply table torque by |
|---|
| Molybdenum disulphide (MoS2) paste | 0.08 - 0.10 | 0.69 |
| Oiled / anti-seize | 0.10 - 0.12 | 0.81 |
| Zinc plated, lightly oiled (table basis) | 0.12 - 0.16 | 1.00 |
| Plain black / phosphated, dry | 0.16 - 0.20 | 1.25 |
| Hot-dip galvanised, dry | 0.20 - 0.25 | 1.5 |
Bolt grade markings
| Marking | Meaning |
|---|
| 8.8 | 1st number × 100 = tensile strength in MPa (800). 2nd number × 10 = yield as % of tensile (80%) |
| Nut 8 / 10 / 12 | Use a nut class at least equal to the bolt's first number |
| A2-70, A4-80 | Stainless: A2 = 304, A4 = 316; 70 / 80 = tensile ÷ 10 in MPa |
| SAE Grade 5 | 3 radial lines on the head (120 ksi tensile) |
| SAE Grade 8 | 6 radial lines on the head (150 ksi tensile) |
These are maximum assembly torques for steel-to-steel joints. Use the equipment maker's figure where one is given, and reduce torque for soft materials (aluminium, plastics), gaskets and tapped holes in cast iron. Re-torque after the first run-in only when the maker says so.
