Stress area: 0.334 in² · Proof load: 40,080 lbs · Clamp load (75%): 30,060 lbs
| Surface Condition | K Factor | ft·lbs | N·m | in·lbs | kgf·cm |
|---|---|---|---|---|---|
| Plain/Dry | 0.2 | 375.8 | 509.5 | 4509.0 | 5194.9 |
| Oiled | 0.15 | 281.8 | 382.1 | 3381.8 | 3896.2 |
| Zinc Plated | 0.18 | 338.2 | 458.5 | 4058.1 | 4675.4 |
| Waxed | 0.1 | 187.9 | 254.8 | 2254.5 | 2597.5 |
| MoS₂ | 0.12 | 225.5 | 305.7 | 2705.4 | 3117.0 |
| Galvanized | 0.25 | 469.7 | 636.8 | 5636.2 | 6493.7 |
Stress area: 0.373 in² · Proof load: 44,760 lbs · Clamp load (75%): 33,570 lbs
| Surface Condition | K Factor | ft·lbs | N·m | in·lbs | kgf·cm |
|---|---|---|---|---|---|
| Plain/Dry | 0.2 | 419.6 | 568.9 | 5035.5 | 5801.5 |
| Oiled | 0.15 | 314.7 | 426.7 | 3776.6 | 4351.1 |
| Zinc Plated | 0.18 | 377.7 | 512.1 | 4531.9 | 5221.4 |
| Waxed | 0.1 | 209.8 | 284.5 | 2517.8 | 2900.8 |
| MoS₂ | 0.12 | 251.8 | 341.4 | 3021.3 | 3480.9 |
| Galvanized | 0.25 | 524.5 | 711.1 | 6294.4 | 7251.9 |
UNC thread, ft·lbs. Values from the table above.
Same bolt, same target clamp load: thread friction alone moves the required torque from 187.9 ft·lbs (waxed) to 469.7 ft·lbs (hot-dip galvanized), 2.5× as much. Match the row to the fastener's actual finish and lubrication.
Formula: T = K × D × F
Step 1 — Clamp load: F = 0.75 × 120,000 psi × 0.334 in² = 30,060 lbs
Step 2 — Torque (dry): T = 0.20 × 0.75 in × 30,060 lbs ÷ 12 = 375.8 ft·lbs
Proof stress per SAE J429 Table 3. Stress area per ASME B1.1. Typical K-factor, consistent with VDI 2230 friction values.
High-strength applications, heavy equipment, critical joints, suspension components, trailer hitches. Equivalent to ISO 10.9.