Washers are very common standard parts. We often find washers during the tightening process of threaded connections such as bolts and nuts. It can even be said that washers are always used in conjunction with threaded fasteners such as bolts or screws.
If the base material is very soft, the surface of the base mother board material will be damaged during the process of screwing in the bolts or screws. By using washers, this squeezing force can be distributed in a larger area to avoid damage to the surface of the motherboard.
If the base material is very soft and the periphery of the hole where the fastener is installed has been damaged, then during the process of screwing in the fastener, the problem of pull-through failure may occur. This is because in most cases, the The force in the process is sufficient to pull the fastener through the material mother board, and the presence of the gasket helps to generate a smaller build-up pressure.
When the surface of the motherboard into which the bolt or screw is screwed is not smooth and flat, the head of the fastener is likely to be stuck. By using a washer, the surface of the bolt or screw can be ensured to slide and make installation easier.
Some washers use a special structural design to prevent the nut from loosening. We commonly call this type of washer a lock washer, and there are many types of structures, such as open type, star type, wave type, and so on. This type of lock washer needs to be used in conjunction with a nut. It can be seen that, except for the specially designed lock washers, the rest of the washers are mostly for distributing the load under the bolt head and nut surface, that is to say, the washers only play a role in dispersing the load for the connection structure.
The reason for the loosening of threaded fasteners after installation is mostly caused by the lateral load, because it will cause the joint to slide, so we always emphasize the importance of pre-tightening force. Adequate pre-load can effectively avoid joints. The problem of relative sliding, thereby avoiding the occurrence of loosening. However, for the installation of threaded fasteners, effectively controlling the pre-tightening force is a very important issue. Even if the thread specifications and installation tools are unchanged, different operators may also cause insufficient pre-tightening force. Happen. In addition, one point that we cannot ignore is that when the washer is used for installation, the washer is not fixed, it can rotate along the axis of the threaded fastener, and this will definitely affect the torque input, and thus affect the Pre-tightening force. In recent years, the use of flange fasteners has gradually increased, because flanges also have the ability to reasonably disperse the load force and eliminate the rotation problem mentioned above, so flange fasteners will gradually replace the application of gaskets.
