BS 4320 is a British Standard specification that outlines the dimensions and tolerances for flat washers for general engineering purposes. Established to ensure consistency and quality across mechanical components, BS 4320 sets precise guidelines for the manufacturing and verification of flat washers made from materials such as steel, stainless steel, and non-ferrous metals. The standard categorizes washers based on their shape and size, thereby facilitating the selection process for specific applications. By adhering to BS 4320, manufacturers and engineers can ensure that washers are compatible with the bolts, screws, and nuts they are intended to be used with, thereby enhancing the reliability and longevity of mechanical assemblies. Compliance with this standard is crucial for products that are intended for use in critical engineering applications, where failure could result in significant consequences.