Guide complet des spécifications de couple de serrage des boulons. Apprenez les valeurs de couple correctes, les méthodes de serrage et le calcul de précharge.
Understanding Torque and Preload
Proper bolt tightening creates clamp force (preload) that holds the joint together: Torque Formula: T = K × F × d Where: - T = Torque (Nm or ft-lb) - K = Nut factor (typically 0.2) - F = Desired preload (N or lb) - d = Nominal bolt diameter (m or ft) Preload Requirements: - Joint design determines required preload - Too little: Joint may separate - Too much: Bolt may yield or fail Typical preload: 60-75% of bolt proof load
Metric Bolt Torque Values
Typical torque values for metric hex bolts: Grade 8.8 Bolts: - M8: 25-30 Nm - M10: 50-60 Nm - M12: 85-95 Nm - M16: 210-240 Nm - M20: 410-460 Nm - M24: 710-800 Nm Grade 10.9 Bolts: - M8: 35-40 Nm - M10: 70-80 Nm - M12: 120-135 Nm - M16: 295-330 Nm - M20: 580-650 Nm - M24: 1000-1100 Nm Note: Values are approximate and depend on lubrication condition.
| Bolt Size | Grade 8.8 Nm | Grade 10.9 Nm | Grade 12.9 Nm |
|---|---|---|---|
| M8 | 25-30 | 35-40 | 40-45 |
| M10 | 50-60 | 70-80 | 80-90 |
| M12 | 85-95 | 120-135 | 140-155 |
| M16 | 210-240 | 295-330 | 345-380 |
| M20 | 410-460 | 580-650 | 680-750 |
Tightening Methods
Different methods for achieving proper preload: 1. Torque Wrench Method: - Most common method - Direct torque measurement - Accuracy ±10-20% - Requires calibrated wrench 2. Angle Turn Method: - Turn bolt specific angle after snug - More accurate than torque - Requires experienced operator - Common: 60-90° after snug 3. Hydraulic Tensioner: - Uses hydraulic pressure - Very accurate preload - Used for large bolts (M36+) - Expensive equipment 4. Combined Method: - Torque to 50-60% of target - Angle turn remaining amount - Best accuracy and repeatability