Washers are thin, disk-shaped plates with holes in the center commonly used in conjunction with a screw or a bolt. The primary function of a washer is to distribute the pressure of the fastener evenly over the surface, thereby reducing the chance of damage to the assembled parts. It also provides a smooth, flat surface for the nut or bolt head to press against, minimizing the risk of loosening over time due to vibration or movement. Moreover, washers can prevent galvanic corrosion by acting as a barrier between different types of metals and can help to seal joints to prevent leakage of fluids.
Washers are versatile and find uses across a multitude of applications ranging from simple household fixes to complex industrial machinery. Their characteristics such as material type (which includes steel, plastic, rubber, and more), shape, and size can significantly influence their suitability for specific tasks. Flat washers, spring washers, and locking washers each serve distinct purposes, from providing a flat bearing surface to prevent bolt or nut heads from tearing into the contacting surface, to preventing fastening or loosening due to vibrational forces. Some of the well-known manufacturers of washers include The Fastenal Company, MSC Industrial Supply Co., among others.