How to Increase the Reuse Cycle of Fastener Bolts and Nuts

How to Increase the Reuse Cycle of Fastener Bolts and Nuts

In the industrial sector, reusing fasteners like bolts and nuts helps reduce costs and increases resource efficiency. So, which bolts and nuts can be reused, and how can we extend their reuse cycle? This article will explore how to optimize bolt usage and enhance their reusability.

（1） Reusability of Bolts Tightened by Torque Method

Bolts tightened by torque are commonly used in high-strength connections, such as railway bridges and building structures. After tightening, the preload of these bolts is influenced by the coefficient of friction, so their reusability depends on how this friction coefficient changes over time.

Factors Affecting Bolt Reuse:

Coefficient of Friction: As bolts are used repeatedly, the friction coefficient between the threads increases, which can lead to instability in the preload force.

Preload Force Variation: The stability of the preload force is key to the reusability of the bolt. By optimizing the friction coefficient, bolts can retain their functionality over multiple uses.

Strategies to Increase Bolt Reusability:

1. Increase the Lubricant Layer Thickness: The friction force acts primarily on the lubrication layer during tightening. Regular lubrication or increasing the thickness of the lubricant layer can reduce thread wear and stabilize the friction coefficient.

2. Reduce Bolt Usage Rate: Overusing bolts can wear down the lubrication layer quickly and affect the stability of the preload force. By lowering the bolt usage rate, the reusability of bolts can be significantly extended.

3 .Use Precise Tightening Tools: High-precision tightening tools can help control the friction coefficient variation, ensuring that preload force remains stable and the bolts can be reused multiple times.

（2） Bolts Tightened by Torque-Angle Method Beyond Yield Point

In some applications, bolts are tightened beyond their yield point, known as the torque-angle method yield. Once a bolt reaches the yield point, it cannot return to its original state, limiting its reuse cycle.

Limitations of Beyond-Yield Bolts:

Plastic Deformation: Bolts tightened beyond the yield point undergo plastic deformation, preventing the preload force from being restored. Typically, they can only be used once.

Thin Bolts: Because the angle of deformation is smaller for thin bolts, they may withstand a few more uses. However, excessive yield tightening should be avoided.

（3）Reusability of Self-Locking Nuts

Self-locking nuts (such as nylon lock nuts) are widely used for anti-loosening applications. Due to the nylon insert or elliptical threads inside the nut, the locking effect decreases after repeated use.

Limitations of Self-Locking Nuts:

Self-locking nuts are typically usable up to 5 times. After that, their anti-loosening ability diminishes, although they can still provide some locking function.

（4） Limitations of Microencapsulated Chemical Adhesive Fasteners

Microencapsulated chemical adhesive fasteners use glue that combines with the thread pair after the microcapsules break open during tightening. Once cured, the adhesive provides a strong anti-loosening effect. However, the adhesive cannot be reactivated after disassembly, limiting its reuse.

Usage Limitations of Microencapsulated Fasteners:

These fasteners are generally single-use. After loosening, the adhesive no longer provides effective locking, and the fastener must be replaced.

（5）How to Reduce Thread Wear and Extend Fastener Life

Use Proper Removal Tools:

Using professional bolt removal tools can prevent excessive damage to the threads. Improper handling, such as hitting the bolt with a hammer, can damage the threads, reducing the bolt's reusability.

Improve Bolt Design:

Improving bolt design, such as refining the bolt end, can reduce thread damage during disassembly and increase the bolt's reusability

Use Thread Locking Adhesives:

Applying thread-locking adhesives between nuts and bolts can increase the connection strength and reduce wear caused by loosening, further extending their reuse cycle.

（6）Conclusion: How to Increase the Reuse of Fastener Bolts and Nuts

Bolts tightened by torque method: Regular lubrication, reduced usage rate, and precise tightening tools.

Bolts tightened beyond yield: Generally, bolts can only be used once. Thin bolts may withstand additional uses, but excessive yield tightening should be avoided.

Self-locking nuts: These can be used up to 5 times before losing their anti-loosening ability.

Microencapsulated chemical adhesive fasteners are single-use only and must be replaced after loosening.

By applying proper design, lubrication, and tools, you can significantly extend the reuse cycle of fasteners, prolong the life of bolts, reduce overall costs, and enhance the reliability of industrial connections.

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