This International Standard specifies the requirements for metric screw and plain washer assemblies made of steel with coarse thread M2 to M12 inclusive, flat seating heads, property classes up to and including 10.9 and washer hardness classes 200 HV or 300 HV. The plain washers are captive, i.e. prevented from disassembly and free to rotate. NOTE The manufacturing of screw and washer assemblies takes into consideration material and production procedure of screw blank and washer as well as the assembly process of components, in order to meet specification requirements (see Annex A).