Technical aspects and scope of application for EN ISO 7091 washers
The international standard EN ISO 7091 regulates the geometry and technical requirements for plain washers of the normal series, belonging to product grade C with a hardness of 100 HV. This fastener is designed for use with metric threaded connections having nominal diameters from 1.6 to 64 mm.
The engineering department of EV Group China recommends using washers of this category in the following assemblies:
- Hexagon bolts and screws of product grade C with a property class not exceeding 6.8.
- Hexagon nuts corresponding to property classes up to and including 6.
- Thread-rolled hardened screws.
When selecting sizes not covered by the EN ISO 7091 standard, one should be guided by the ISO 887 specifications, which contain an extended nomenclature of normal plain washers.
Important note for design engineers: when working with soft base materials or in the presence of oversized mounting holes in mating parts, EV Group China specialists recommend performing a preliminary calculation of contact stresses to confirm the suitability of 100 HV grade washers. Incorrect selection can lead to surface deformation or loss of preload in the joint.