USS Flat Washer, Galvanized
Low carbon USS flat washers are used under bolt heads or nuts to increase the bearing surface area, or to offer protection so that the nut or bolt can be rotated without distortion of the bearing surface. Flat washers are also used to give tightness to a joint, to prevent leakage, and especially to distribute pressure under the head of a bolt or nut. Dimensional specifications are governed by ASME B18.21.1. USS (United States Standard) flat washers have a larger outer diameter than structural ASTM F436 flat washers, and can be utilized in nearly any application. ASTM F844 covers the standard specifications for unhardened steel flat washers for general use. Hot dip galvanizing provides a highly corrosion resistant finish, made of sacrificial zinc.