Plain washers, standard and custom

The plain washers which are adequate for simple applications are those covered by DIN125 (ISO7089-7090, with & without chamfer), with bare steel or zinc plate coating. The same washers can also be hardened at 200HV for more demanding applications. The DIN6916 washers made from C45 are best for steel structures (joints with high-tensile, pre-stressed bolts). Similar standards are the washers covered by ISO7415/7416 (plain washers with or without chamfered, for high structural bolting, hardened and tempered).

Another plain washer standard is the DIN6340 (plain washers, hardened). The washers according to DIN6340 are made from C35 and they are also recommended for high stressed applications.

The high strength washers are very useful for high strength bolts and assemblies. There are many applications where the DIN125 zinc plated washers cannot tolerate the compression forces and collapse. Another advantage is that they have longer operating time (time-to-failure) between maintenance and disassemblies. They are used in machine tool construction, special tooling, jigs and fixtures. Both faces of the washer have a roughness of Ra 2.5. Another good solution is the manufacture of custom washers made from heat treatable steel 34CrNiMo6, which is deliverable in a hardened state. The steel 34CrNiMo6 has enough strength for the bolt-nut assembly without being subjected to further hardening.
The hardened plain washers are prerequisite in industrial machinery and for this reason there are many standards covering all the needs. Heat treatable steels are best for custom washers.