Support washers DIN 988-spring steel hardened plain 90x110x3,5

Flat washers are available in different hardness classes. The combination of strength classes of flat washers with strength classes of screws and nuts is regulated according to ISO 898-3:2018, Table 1. Washers with a hardness of 440 HV are suitable for applications with tempered screws and nuts (screws up to 12.9, nuts up to class 12).

Spring steel is a steel that has a higher strength compared to other steels, but with very high elasticity. Tension discs and disc springs are made of spring steel so that the spring forces defined in the standard can be achieved.

The term plain indicates a completely untreated, merely oiled, smooth surface for all DIN and ISO screws such as wood screws, hexagon head screws, threaded rods, nuts and many types of washers.