Generally, washers are defined as thin disc-shaped plates, typically with a hole through the center, that are used in conjunction with a threaded fastener such as a screw or a bolt. The usual functions of washers include distributing load, creating separation, preventing corrosion and wear, locking fasteners, and reduce vibration.
A flat washer, also known as a plain washer, is a type of washer that is a flat annulus or ring which is used to spread the load of a screwed fastener and prevent damage to the surface being fixed. F436 Flat Washer is a heat-treated washer which is for general purposes and structural use. It is well suited to be used with other specification fasteners like the A325 and A490 structural bolts.
F436 Material Grade are hardened flat washers which have a Rockwell Hardness value ranging between 38 to 45 HRC. This F436 flat washer is used under bolt nuts and head to increase the bearing area. It is hard enough so that the bolt or the nut used can be rotated without the surface of the bearing being distorted.