Flat washers are typically thin pieces of various shapes used to reduce friction, prevent leaks, isolate, prevent loosening, or distribute pressure. Such components are found in many materials and structures and serve a variety of similar functions. Due to the material and process limitations of threaded fasteners, the supporting surface of bolts and other fasteners is not large. Therefore, in order to reduce the compressive stress on the pressure-bearing surface and protect the surface of the connected parts, washers are used. In order to prevent the connection pair from loosening, anti-loosening spring washers and multi-tooth lock washers, round nut stop washers and saddle-shaped, wave-shaped and tapered elastic washers are used.

Flat washers are mainly used to reduce pressure. When the axial force of tightening in some parts is very large, it is easy to press the washers into a disc shape. At this time, the material can be changed and the hardness can be increased to solve the problem.