Bolt Tightening - Torque versus Tension

In summary, bolt tightening involves using torque or tension to secure bolts in place. Torque measures the rotational force applied to the bolt, while tension measures the stretching force on the bolt. Both methods are important in ensuring proper bolt tightening and preventing loosening or failure. Torque is commonly used for larger bolts and tension for smaller bolts. It is important to follow manufacturer specifications and use the correct tools to achieve the desired torque or tension for a secure bolt joint.
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clurt
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Hi guys,

Bringing myself back up to speed with bolt tightening, would really appreciate if anyone has some resources or answers to these questions:

1. The proof load for torque tightening, and proof load for tension tightening
2. Main advantages and disadvantages between the two
3. What is the equivalence between the two. For example... M48 Bolt was tensioned to using 750kN of force, now this is unavailable. What is the torque required to achieve the equivalent tightening, 5000Nm, 6000Nm?
4. Is proof load related to the force that a bolt is tensioned?
5. What are the stresses in bolt tensioning. Is it a percentage of the yield strength?
6. Difference between bolt being stressed and bolt force?
7. Is there an equation that can translate tension and torque tightening, vice versa.

Thanks
 
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1. What is the difference between torque and tension when tightening bolts?

Torque is a measure of the rotational force applied to a bolt, while tension is the resulting stretching force on the bolt. Torque is typically measured in units of foot-pounds or Newton-meters, while tension is measured in units of pounds or Newtons.

2. Which is more important in bolt tightening - torque or tension?

Both torque and tension are important in bolt tightening. Torque ensures that the bolt is properly secured and will not loosen over time. Tension helps to evenly distribute the load on the bolt and prevent it from breaking under stress. It is important to follow the recommended torque and tension specifications for your specific application.

3. How do I determine the correct torque and tension for a bolt?

The correct torque and tension for a bolt depends on factors such as the size and grade of the bolt, the material of the bolt and the material it is being secured to, and the application. Consult the manufacturer's specifications or a torque/tension chart for your specific bolt and application.

4. What happens if I over-torque or under-torque a bolt?

If a bolt is over-torqued, it can lead to excessive tension, which can cause the bolt to break or strip the threads. Under-torquing a bolt can result in insufficient tension, which can lead to the bolt loosening over time. It is important to use the correct torque and tension specifications to ensure proper bolt tightening.

5. Can I reuse a bolt after it has been tightened?

The ability to reuse a bolt after it has been tightened depends on several factors, such as the material and grade of the bolt, the application, and the amount of torque and tension applied. It is generally recommended to replace bolts after they have been tightened, but if they are in good condition and within the recommended torque/tension specifications, they may be reused.

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