Washer is to pad in the fitting between the nut and parts. For flat shape of the metal ring, commonly used to protect by fitting the surface of the nut scratches, scattered nut on the fitting of a pressure.

Flat washer is generally used in fitting a soft texture, is a hard, brittle, its main role is increasing contact area and pressure, to prevent the quality of a material soft crush. Spring washer and spring is the basic function of after nut tighten nut to a force, increase the friction between the nut and bolt! Material is 65 Mn (spring steel), heat treatment is HRC44 – 51 HRC hardness, the surface oxidation treatment.