Threaded fasteners are mechanical parts with internal or external threads. They are generally used as fasteners to facilitate the combination of multiple components. The most common threaded fasteners are screws, nuts and bolts. However, there are other threaded fasteners, such as cage nuts, threaded inserts, threaded rods, etc.

Threaded fasteners are used in almost all mechanical equipment. Therefore, threaded connection technology is one of the most important technologies to ensure the reliability of mechanical systems. Due to frequent use, threaded fasteners have become one of the most standardized components. General standards such as ISO and JIS have provided parts catalog tables of bolts, nuts, washers, etc. according to their size (nominal diameter, length, head shape, etc.) and strength class. Therefore, you only need to choose from the standard, and threaded fasteners of any specification are easy to use. The result is that threaded fasteners have become a very simple part, which can be "designed" through "simple choice".