The primary purpose of a washer in a fastener assembly is to distribute the load of the fastener, reducing stress on the material and protecting the surface from damage. By spreading the load, washers help prevent the fastener from pulling through or causing dents in softer materials. They also act as a barrier to reduce friction between the fastener and surface, ensuring a secure and stable connection that is less likely to loosen over time.

Lock washers differ from flat washers in that they are specifically designed to prevent fasteners from loosening due to vibration or movement. While flat washers focus on load distribution, lock washers have a helical or split design that creates tension, holding the fastener securely in place. This makes lock washers ideal for applications with dynamic loads or machinery with frequent vibrations, where maintaining a tight, secure connection is essential.

Washers are made from different materials like metal, rubber, and nylon to suit various application needs and environmental conditions. Metal washers, like those made of stainless steel, are strong and durable, ideal for heavy-duty applications. Rubber washers provide cushioning, vibration absorption, and water sealing, making them useful in plumbing or damp environments. Nylon washers offer insulation and are non-conductive, making them suitable for electronic applications or where electrical insulation is required. Each material is selected based on its unique properties to enhance performance in specific applications.