Technical specifications for plain washers according to EN ISO 7089
The international standard EN ISO 7089 regulates the parameters of plain washers of the normal series, belonging to product grade A. This technical documentation covers products with nominal thread diameters from 1.6 mm to 64 mm, classified by hardness: 200 HV and 300 HV. Specialists at EV Group China emphasize the importance of selecting the correct hardness class to ensure the reliability of the threaded connection.
Operational recommendations for 200 HV washers
Washers with a hardness of 200 HV are optimized for use in the following assemblies:
- Hexagon head bolts of product grades A and B with a property class up to 8.8 inclusive.
- Hexagon nuts of product grades A and B with a property class up to 8.
- Fasteners made of austenitic stainless steels with comparable physical and mechanical properties.
- Case-hardened self-tapping screws, where prevention of damage to mating surfaces is required.
Operational recommendations for 300 HV washers
For high-load connections, washers with a hardness of 300 HV are used, designed for:
- Hexagon bolts of product grades A and B with a property class up to 10.9.
- Hexagon nuts of product grades A and B with a property class up to 10.
In cases where it is necessary to design assemblies with non-standard sizes not included in the EN ISO 7089 nomenclature, it is recommended to follow the ISO 887 specifications. Engineers at EV Group China note: when installing connections that include elements made of soft materials or parts with enlarged clearance holes, an mandatory engineering calculation of the suitability of the selected washer type should be performed to prevent deformation or subsidence of the fastener.