Fastening function
The nut is used in conjunction with the bolt. By tightening the nut, an axial force is generated to tightly connect the various parts of the fastener together. Ensure that the railway fastener will not loosen during train operation and maintain the geometric shape and stability of the track.
For example, when a high-speed train is running, strong centrifugal force and vibration will exert a huge force on the track. If the nut is loose, the connection strength of the fastener will be greatly reduced, which may lead to serious consequences such as rail displacement and gauge change, endangering the safe operation of the train.

Anti-loosening function
In order to prevent the nut from loosening during train vibration and long-term use, some anti-loosening measures are usually adopted, such as using spring washers, double nuts, etc. These measures can increase the friction between the nut and the bolt and prevent the nut from loosening on its own.
Once the nut is loose, it will not only affect the stability of the track, but also may cause the bolt to fall off, causing a serious safety accident. Therefore, the anti-loosening function of the nut is extremely important.

Adjusting function
During the installation and maintenance of railway fasteners, the tightness of the fastener can be adjusted by adjusting the tightening degree of the nut. Thus, fine-tuning of track geometric parameters such as gauge and height can be achieved.
For example, when it is found that the gauge is too large or too small, by properly tightening or loosening the nut, the relative position between the fastener and the rail can be adjusted to restore the gauge to the standard value. This is of great significance for ensuring the smooth running of the train and improving ride comfort.