Quick-reference torque values for M42 bolts across all property classes. Values shown for dry/plain steel, coarse thread. Click any card for full details including all surface conditions.
These values assume dry/plain steel (K = 0.20) and coarse thread. Oiled, zinc-plated, or lubricated bolts require different torque. See full details →
For a typical M42 class 8.8 bolt the dry figure is 4237.0 N·m (3125.1 ft·lbs). If the threads are oiled, drop to 3177.8 N·m — using the dry number on an oiled bolt would push it about 33% past the intended clamp load. Class 10.9 takes 5861.2 N·m, 38% more than 8.8, and the fine M42×3.0 thread raises the 8.8 figure to 4557.5 N·m because its stress area is 8% larger.
At M42 the torque figures run into the thousands of N·m, past the range of hand tools. Bolts this size are normally tightened with hydraulic torque wrenches or, preferably, hydraulic bolt tensioners that stretch the bolt directly and take friction out of the equation. Treat the values below as a cross-check for the tensioning procedure rather than as the primary method; ISO 898-1 still applies up to M64 for the property classes shown.
N·m. Coarse thread unless noted. Clamp load is the 75%-of-proof preload the torque is sized to produce.
| Coarse thread | M42×4.5 |
| Fine thread | M42×3.0 |
| Stress area (coarse / fine) | 1120.9 / 1205.7 mm² |
| Hex wrench size | 65 mm (ISO 4032) |
| Tap drill (coarse / fine) | 37.5 mm / 39 mm |
| Clearance hole (ISO 273 medium) | 45 mm |
Pitches per ISO 261/262; stress area per ISO 898-1; tap drill = nominal diameter minus pitch. M42 coarse vs fine →