Flat Washer Plain Washer Blue Color Anodizing Metric SAE USS

A flat washer is a flat annulus or ring, often of metal, used to spread the load of a screwed fastening. Additionally, a flat washer may be used when the hole is a larger diameter than the fixing nut. Ever Hardware provides custom-made fasteners and customizable packaging.

A flat washer is a thin plate (typically disk-shaped) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a screw or nut. Other uses are as a spacer, spring (Belleville washer, wave washer), wear pad, preload indicating device, locking device, and to reduce vibration (rubber washer). Washers usually have an outer diameter (OD) about twice larger than their inner diameter (ID).

Washers are usually metal or plastic. High-quality bolted joints require hardened steel washers to prevent the loss of pre-load due to Brinelling after the torque is applied.

Rubber or fiber gaskets used in taps (or faucets, or valves) to stop the flow of water are sometimes referred to colloquially as washers; but, while they may look similar, washers and gaskets are usually designed for different functions and made differently.

Washers are also important for preventing galvanic corrosion, particularly by insulating steel screws from aluminum surfaces.