Bolts in rail systems
In the rail system, bolts are widely used, covering multiple key parts such as fasteners, joints, turnouts, and guardrails. Although these application scenarios are clear, our focus is not only on this. By mentioning the ubiquity of bolts in the rail system, we can more deeply feel its indispensable importance.
Because we are well aware of the importance of bolts in the rail system, there is no need to elaborate on their ubiquity. Commonly used bolts can be roughly divided into carbon steel, stainless steel, copper, and aluminum according to their materials. Copper bolts are often associated with electrical connections, while aluminum bolts are more common in automobile and locomotive manufacturing and are relatively less used on rails. As for the type of thread, its classification is relatively complex. According to the position of the thread, it can be divided into internal thread and external thread. For example, the screw is provided with external thread (that is, the thread is located on the outside), while the nut is provided with internal thread.
Bolts are usually provided with external threads, while nuts are provided with internal threads. In addition, according to the direction of the thread, bolts and nuts can be further subdivided into left-handed threads and right-handed threads. It is worth noting that most bolts use right-hand threads, that is, they are tightened in a clockwise direction and loosened in a counterclockwise direction. This design is more in line with people's habits and makes the tightening process more convenient. However, there are some special cases, such as the bolts on some rail saws, which need to be kept tightened when the saw blade rotates, so the left-hand thread design is adopted.
After discussing the thread direction of bolts and nuts, we go further and classify threads from the perspective of tooth profile. Tooth profile, that is, the cross-sectional shape of the thread, is one of the important characteristics of the thread. According to the tooth profile, threads can be divided into triangular threads, trapezoidal threads, rectangular threads, serrated threads and circular threads. Among them, triangular threads are widely used in various occasions due to their unique connection function, especially in rail connections, where they are the most common thread tooth profile. A simple way to judge is that when a bolt and a metal nut are tightened together, a triangular thread is usually used.
