Product Introduction
CE-marked high-strength structural bolting assemblies manufactured to EN 14399-3 for System HR (Hexagon head with Reinforcement). Designed for preloaded joints in steel structures to Eurocode 3 (EN 1993-1-8), each assembly includes a property class 10.9 hexagon bolt with large widths across flats, a property class 10 hexagon nut, and through-hardened washers to EN 14399-6. Sizes M12 to M36. HR assemblies achieve preload by bolt elongation, offering controlled ductility and insensitivity to moderate overtightening.

Thread Tolerance & Hot-Dip Galvanizing
Bolts are threaded before hot-dip galvanizing to tolerance class 6az per ISO 965-5, providing an oversize allowance that accommodates the zinc coating thickness (typically 40–80 μm). After galvanizing, the external thread mates correctly with internal thread tolerance 6H. Nuts to property class 10 feature 6H (or 6AZ if galvanized) internal threads with a proof load stress of 1160 MPa.

Mechanical Properties & Thread Length
Bolts conform to EN ISO 898-1 property class 10.9: minimum tensile strength 1000 MPa, yield strength 900 MPa. Nuts are property class 10 to EN ISO 898-2, style 1 normal height per EN ISO 4032. Thread length follows ISO 888—longer than standard—so preload reaches at least 0.7 × fub × As (70% of ultimate tensile load). This geometry ensures ductility through plastic elongation of the bolt shank; bolt breakage during tensioning is the designated failure mode, providing a clear indication of over-tension.

Washers & Assembly Compliance
Washers are supplied under the nut only, conforming to EN 14399-6: Vickers hardness 300–370 HV, through-hardened to distribute preload and prevent embedment. The complete hot-dip galvanized assembly complies with EN ISO 10684 for coating durability and EN 1090-2 for preloaded joint installation. Every component carries traceability codes and is backed by batch-specific inspection certificate 3.1 per EN 10204.