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
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Metric Bolt Torque Values
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| 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
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Questions Fréquemment Posées
See frequently asked questions below.
What torque should I use for M10 bolt Grade 8.8?
For M10 Grade 8.8 hex bolts, the recommended torque is 50-60 Nm (37-44 ft-lb). For Grade 10.9, use 70-80 Nm (52-59 ft-lb). Always refer to your specific application requirements.
What is the difference between preload and torque?
Torque is the rotational force applied to tighten a bolt. Preload (clamp force) is the tension created in the bolt when tightened. The goal is to achieve correct preload; torque is just the method to reach it.
Can torque specification bolts be reused after loosening?
Generally no. Once a bolt has been torqued beyond its yield point and then loosened, it may have been permanently stretched. Replace with new bolts for critical structural applications.
What is the nut factor (K) in torque calculation?
The nut factor K accounts for friction in the torque-tension relationship. K = 0.2 is commonly used for plain (unlubricated) bolts. For lubricated bolts, K may be 0.15-0.18. Always check with your specific coating/lubrication condition.
How do I know if a bolt is properly tightened?
Use a calibrated torque wrench set to the correct specification. For critical joints, use direct tension indicators (washers with raised bumps) or ultrasonic bolt stretch measurement.