What is the Importance and Working Principle of Fasteners?

As a Rail Bolt Manufacturer, share with you.

High Strength Bridge Bolt

1. The importance of fasteners

If the force is too small, the washer may not be in place; if the force is too much, the thread will be worn. According to recently published data, 23% of maintenance problems in the automotive industry are caused by loose fasteners, and 12% of new cars have incorrect fastener tightness. Bolts are one of the most important factors that determine the quality of assembly. The failure of threaded fasteners to reach the corresponding capacity is an important cause of assembly accidents!

2. The principle of tightening fastener bolts

The bolt connection must be able to resist external force, so that the assembled parts will not move in the direction of separation, otherwise it will cause the bolt joint to loosen, damage or fall off.

Therefore, we design the minimum clamping force of the bolt to prevent the clamping part from being separated due to external force, and to maintain friction clamping or ensure sealing, etc.

The bolt is inserted into the connected part, and the bolt is stretched and deformed by tightening the nut or internal thread. This elastic deformation produces an axial pulling force that squeezes the clamped parts together, which is called pre-tightening force.

In theory, as long as sufficient clamping force is generated, the clamped parts can be guaranteed to work safely in harsh environments such as vibration, high and low temperatures, without using auxiliary methods such as glue coating.

3. Clamping force of fasteners

The only purpose of the tightening procedure is to maintain the clamping force within the corresponding tolerance range!

During assembly, the clamping force must be large enough to ensure that the assembled parts will never move relative to each other. But at the same time, it must be ensured that the clamping force applied during tightening does not cause damage or plastic deformation of the bolt.

Clamping force control is the core purpose of bolt assembly. Improper clamping force control will cause serious consequences.

4. Torque distribution

By applying oil on the surface of the fastener, friction can be reduced and the pre-tightening force can be increased under the same torque. In other words, to achieve the same tightening effect, the torque required for the oiled bolt should be small.

Torque detection method:

① Loosening method: It needs to be tightened after loosening, which is troublesome and rarely used;

② Fastening method: the most commonly used, the detection torque is larger than the actual tightening torque;

③ Marking method: the most accurate, complicated operation, rarely used.

5. Commonly used tightening methods for fasteners

Torque control method: is the most widely used tightening method, suitable for most non-critical parts of the bolt connection.

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