What is the role of a cotter pin in a bolted joint?

A cotter pin plays a crucial role in fastening systems, particularly in bolted joints, by securing the nut in place and preventing it from loosening due to vibrations or operational loads. When a cotter pin is inserted through a hole in the bolt after the nut is tightened, it creates a mechanical lock. This locking mechanism is vital in applications where joint integrity is essential, as it ensures the nut cannot rotate or back off on its own.

This use of cotter pins is particularly common in various machinery and automotive applications, where maintaining a stable and secure connection is critical for safety and performance. By providing this extra layer of security, cotter pins help in maintaining the overall reliability of the bolted assembly.