Thrust washers are used as a bearing surface for rotary applications. They are usually made of steel, bronze, plastic, or other material with low friction coefficients. Thrust washers, sometimes called rotary thrust washers, are washers designed to prevent movement along the axis of a shaft. Thrust bearings support an axial load on a shaft. A thrust bearing can be a plate at the end of a shaft, or a device against which a collar on the shaft presses. Banded thrust bearings and washers are reinforced by a band encircling the outer edge. Precision-engineered thrust washers are used in high-wear applications such as transmissions, power take-offs, pumps, axle assemblies, motors, and winches. Thrust washer kits contain thrust washers of varying thicknesses for correct installation during component assembly. Standard thrust washers are made for products such as automotive engines. Thrust washer manufactures are located across the United States and around the world,
Thrust washers can be made from case-hardened steel, through-hardened steel, stainless steel, bronze, phosphorous bronze, and brass. Graphite is used in high-temperature applications. Plastics are used for low speeds and light loads. Rubber and lignum vitae are used in water-lubricated bearings. Thrust washers can be made in standard thicknesses, with various inside and outside diameters as needed. Important considerations include flatness and parallelism requirements, surface finish, heat treatment, through-hardness, passivating, and plating.
Standards for Thrust Washers
Various national and international organizations maintain and publish standards for thrust washers. The International Organization for Standardization (ISO) maintains Standard 3031, which covers boundary dimensions and tolerances for thrust washers. ASTM International (formerly called the American Society for Testing and Materials) maintains D 3702, a standard test method for self-lubricated rubbing contact using a thrust washer. The Society of Automotive Engineers (SAE) maintains standard AMS-H-6875, which covers the heat treatment of steel raw materials and stainless steel thrust washers.