Washers are mainly used as a seat to distribute the load, but they can also provide spring tension, cover oversized holes, insulate, seal or provide electrical connections. The different types include flat, conical, and helical washers toothed or splined lock washers, and special washers. Flat washers, also called plain washers, provide a bearing surface for a nut or screw head, cover large through holes and distribute fastener loads over a large area, especially soft materials.
Types of washers
- Type A is a series of steel washers with broad tolerances, where design refinement is not important. They range from No. 6 to 3-in. the whole size and from 3/16 to 5-in. OD. Type A washers are satisfactory for most assemblies.
- Type B washers are premium quality and are specified in narrow, regular, and wide diameters for each screw size from 0 to 3 inches. In addition, many other standard sizes are available. Conical spring washers are used with screws to add spring take-up to screw elongation.
- L-type taper washers are designed for use with unhardened screws.
- Type H series is for hardened screws. Taper washers are designed to flatten to approximately half of the screw’s maximum load.
Application of Washers
- Duplex Steel S32205 are made of slightly trapezoidal wire formed into a spiral helix so that the free height is almost double the thickness of the cross-section. Generally, They are usually made of hardened carbon steel but are also made of aluminum.
- Tooth lock washers are used with screws and nuts to add spring take-up to the screw elongation and to increase frictional resistance under the screw head or nut face. They bite into both the head of the screw and the work surface to provide an interference lock. Even at zero tension, the tooth lock washer provides frictional resistance to loosening.
- Rib washers (serrated safety washers) combine the significant spring properties of conical spring washers with the increased frictional resistance of tooth lock washers. They are available in a variety of materials.
- Special-purpose washers, such as the finishing washer, eliminate the need for a countersunk hole and are used extensively for attaching fabric coverings. The outer rim grips the material over a large area.
- The fairing washer, an aircraft development, is used with flat-head screws on aluminum sinks. Holding pressure is spread over a large area, eliminating localized strains around the screws. The shape of this washer allows for flush surfaces.