Old engineers are not necessarily fully aware of bolting knowledge

1. When using a thick and thin nut to prevent loosening, the thin nut should be placed underneath, and most people use it instead, but to prevent misuse, it is now recommended to use two identical nuts.

Thin nut preload force drop speed at different positions

2. When you flatten the washer, are you free to put it, in fact, the side that is not marked should be in contact with the nut.

The nut is not screwed to the bolt at random. The side of the nut with the marking needs to be exposed, so that it is easy to follow the inspection nut.

3. It is better to use spring washers for bolts that need to be pre-tightened at class 8.8 and above. Experiments have shown that the anti-loose effect of spring washers in pre-tightening bolts is relatively poor, and it will cause a rapid decrease in pre-tightening force. .

4. The bolted contact surfaces are not painted. The paint will increase the stress relaxation of the bolt, that is, the prestress of the bolt will decrease over time.

5. The structure is bolted. When bolts are selected, the bolt size should not be less than M12.

6. When tightening the high-strength pre-tightening bolt with the torque method, if the washer that comes into contact with the nut rotates with the nut when tightening the nut, the connection is invalid because the bolt manufacturer guarantees the nut when producing the bolt set. The frictional resistance with the washer member, the coefficient of friction between the washer and the connector is unknown, and therefore the correspondence between the tightening torque and the preload is also unknown. Therefore, it is necessary to replace the bolt set.

7. When the bolt is tightened, it cannot be tightened to the final torque at one time unless all the bolts at the joint are tightened at the same time.

8. When the bolt is tightened, the speed of tightening the nut should not be too fast. If it is screwed too fast, it will affect the friction coefficient between the screw threads.

9. When tightening the bolts, high-strength bolts are required without relubrication, because the bolt assemblies that are required are all lubricated by the bolt manufacturer, and they guarantee the torque coefficient of the bolts.

10. In the bolted connection, after the nut is tightened, the exposed length of the screw should be around 2 to 3 buckles.

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