Stress area: 0.606 in² · Proof load: 19,998 lbs · Clamp load (75%): 14,998 lbs
| Surface Condition | K Factor | ft·lbs | N·m | in·lbs | kgf·cm |
|---|---|---|---|---|---|
| Plain/Dry | 0.2 | 250.0 | 339.0 | 2999.7 | 3456.0 |
| Oiled | 0.15 | 187.5 | 254.2 | 2249.8 | 2592.0 |
| Zinc Plated | 0.18 | 225.0 | 305.1 | 2699.7 | 3110.4 |
| Waxed | 0.1 | 125.0 | 169.5 | 1499.9 | 1728.0 |
| MoS₂ | 0.12 | 150.0 | 203.4 | 1799.8 | 2073.6 |
| Galvanized | 0.25 | 312.5 | 423.7 | 3749.6 | 4320.0 |
Stress area: 0.663 in² · Proof load: 21,879 lbs · Clamp load (75%): 16,409 lbs
| Surface Condition | K Factor | ft·lbs | N·m | in·lbs | kgf·cm |
|---|---|---|---|---|---|
| Plain/Dry | 0.2 | 273.5 | 370.8 | 3281.9 | 3781.1 |
| Oiled | 0.15 | 205.1 | 278.1 | 2461.4 | 2835.8 |
| Zinc Plated | 0.18 | 246.1 | 333.7 | 2953.7 | 3403.0 |
| Waxed | 0.1 | 136.7 | 185.3 | 1640.9 | 1890.6 |
| MoS₂ | 0.12 | 164.1 | 222.5 | 1969.1 | 2268.7 |
| Galvanized | 0.25 | 341.9 | 463.6 | 4102.3 | 4726.4 |
UNC thread, ft·lbs. Values from the table above.
Same bolt, same target clamp load: thread friction alone moves the required torque from 125.0 ft·lbs (waxed) to 312.5 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 × 33,000 psi × 0.606 in² = 14,998 lbs
Step 2 — Torque (dry): T = 0.20 × 1.0 in × 14,998 lbs ÷ 12 = 250.0 ft·lbs
Proof stress per SAE J429 Table 3. Stress area per ASME B1.1. Typical K-factor, consistent with VDI 2230 friction values.
Large general-purpose bolts, same grade but reduced strength at larger diameters