ISO 4017 Hexagon Head Bolts, Fully Threaded | M5–M56, Property Class 8.8

Product Introduction
Metric hexagon head bolts manufactured to ISO 4017:2022 (superseding DIN 933), with a fully threaded shank extending from under the head to the tip. Thread sizes M5 to M56 in ISO metric coarse pitch, tolerance class 6g. The full-thread configuration permits maximum engagement in tapped blind holes, accommodates variable grip lengths, and simplifies inventory by allowing field cutting. Used in machinery assemblies, structural steelwork, automotive components, and general industrial fastening.

Material & Mechanical Properties
Medium carbon steel, quenched and tempered to property class 8.8 per ISO 898-1. Minimum tensile strength: 800 MPa for M5–M16; 830 MPa for M17–M56. Minimum yield strength: 640 MPa for M5–M16; 660 MPa for M17–M56. Hardness: 250–320 HV. Where specified, total friction coefficient μ = 0.12–0.18 for fasteners with nominal tensile strength ≥ 800 MPa. Stainless steel variants conform to A2-70 (304, 700 MPa) and A4-80 (316, 800 MPa) per ISO 3506-1.

Geometry & Thread
Product grade A applies to threads up to M24 with nominal lengths ≤ 10d or 150 mm, whichever is shorter; grade B applies to larger threads or longer lengths. Width across flats: M5 = 8.0 mm, M6 = 10.0 mm, M8 = 13.0 mm, M10 = 16.0 mm, M12 = 18.0 mm, M16 = 24.0 mm, M20 = 30.0 mm, M24 = 36.0 mm, M30 = 46.0 mm, M36 = 55.0 mm, M56 = 85.0 mm. Head height ranges from 3.5 mm (M5) to 35.0 mm (M56). ISO 4017 replaces DIN 933 with revised spanner widths for M10, M12, M14, and M22. Thread length equals the full bolt length under the head.

Surface Finish
Standard finishes: zinc plating (clear, blue, or yellow passivation), hot-dip galvanizing (HDG), black oxide, Dacromet, and Geomet. For hot-dip galvanized bolts, threads are manufactured to tolerance class 6az (undersize) before coating per ISO 10684, ensuring final fit with standard 6H nuts after galvanizing. These coated bolts are designated 8.8U.

Marking & Certification
Each bolt head is permanently marked with the property class (8.8) and the manufacturer’s identification mark. Bolts supplied under EN 15048 for structural bolting also carry the “SB” mark. Full traceability is maintained through lot control. EN 10204 Type 3.1 inspection certificates are available on request, providing chemical analysis, mechanical properties, and heat identification.

Application Suitability
Machinery assemblies, structural steelwork, automotive components, and general industrial fastening. The fully threaded shank is suited to pre-tapped blind holes, through-bolted joints with variable grip lengths, and applications requiring maximum thread engagement. For shear-critical joints where an unthreaded shank across the shear plane is preferred, ISO 4014 partial-thread bolts are recommended