Overview
EN ISO 10644:2009 (equivalent to ISO 10644:2009) defines requirements for metric screw and plain washer assemblies made of steel where the plain washer is captive (prevented from disassembly but free to rotate). The standard covers coarse thread sizes M2 to M12, flat-seating head forms, and fastener property classes up to and including 10.9, with washer hardness classes of 200 HV or 300 HV.
Key topics and technical requirements
- Scope and components
- Applies to metric screw + plain washer assemblies with captive plain washers that can rotate but not be disassembled.
- Thread range: M2 – M12 (coarse thread); head types are those defined in referenced screw standards.
- Washer hardness classes
- Washers specified as 200 HV or 300 HV.
- For screws up to property class 8.8 washers may be 200 HV or 300 HV; for 9.8 and 10.9, washers shall be 300 HV.
- Dimensions and fit
- Washer dimensions follow ISO 10673; assembled screw dimensions generally follow the loose-part screw standards with specific exceptions (reduced shank so washer can rotate, allowance for washer thickness).
- Note on possible interference between washer internal diameter and screw underhead/transition diameter; type U underhead or chamfered washers are recommended to avoid contact traces and torque/clamp-load effects.
- Materials, mechanical properties and testing
- Components must meet the material and mechanical property requirements of the respective product standards; referee testing per ISO 898-1 with the washer removed.
- Coatings
- Coatings conform to ISO 4042 (electroplated), ISO 10683 (zinc flake) and ISO 9717 (phosphate), or by agreement between supplier and purchaser.
- Manufacturing methods
- Annex A describes two production routes: (1) assemble blank + washer, then thread roll and heat-treat; (2) make components separately, heat-treat, then roll threads in hardened condition.
Applications and users
- Who uses EN ISO 10644: manufacturers of captive screw-and-washer fasteners, fastener purchasers, mechanical design engineers, quality inspectors, and procurement/specification writers.
- Typical applications: assemblies requiring captive plain washers for ease of installation, production automation, or secure retention in machinery, automotive components, consumer products and industrial equipment where predefined torque/clamp relationships and washer hardness are important.
Related standards
EN ISO 10644:2009 gives clear, interoperable requirements for captive screw-and-washer assemblies, helping manufacturers and specifiers ensure consistent performance and compatibility across metric fastener products.