DIN 961 Hexagon Head Bolts | Metric Fine Pitch, Fully Threaded

Product Introduction
Metric hexagon head bolts manufactured to DIN 961 (withdrawn; superseded by ISO 8676). Fully threaded shank with metric fine pitch thread. Sizes M8 to M24 with fine pitches including M8×1, M10×1 or M10×1.25, M12×1.25 or M12×1.5, M14×1.5, M16×1.5, M20×1.5, and M24×2. Fine pitch threads increase the minor diameter and thread engagement, improving vibration resistance and permitting precise torque control. Typical applications: automotive engines, hydraulic systems, high‑pressure fluid connections, and precision machinery.

Material & Mechanical Properties
Medium carbon steel or alloy steel, quenched and tempered to ISO 898‑1.

• Class 8.8: tensile strength ≥800 MPa, yield ≥640 MPa, hardness 22–32 HRC.

• Class 10.9: tensile strength ≥1040 MPa, yield ≥940 MPa, hardness 32–39 HRC.

• Class 12.9 available for maximum strength requirements.
  For fasteners with nominal tensile strength ≥800 MPa, friction coefficient μ total = 0.12–0.18. Thread tolerance 6g for plain finish, 6h for plated finish. Mechanical properties certified by lot; mill test reports available.

Geometry & Thread
Product grade A applies to threads up to M24 with lengths ≤10d or 150 mm, whichever is shorter; grade B for larger. Width across flats: M8 = 13.0 mm, M10 = 17.0 mm, M12 = 19.0 mm, M14 = 22.0 mm, M16 = 24.0 mm, M20 = 30.0 mm, M24 = 36.0 mm. Head height ranges from 5.3 mm (M8) to 15.0 mm (M24). Thread length equals full bolt length under head. ISO 8676 supersedes DIN 961 with revised widths across flats for M10, M12, M14, and M22; however, M10, M12, and M14 fine pitch sizes are only available per DIN 961, as ISO 8676 does not cover these diameters. Coarse thread equivalent: ISO 4017.

Surface Finish
Zinc plating (clear, blue, yellow), black oxide, hot‑dip galvanizing (HDG), Dacromet, Geomet. For HDG, threads manufactured to tolerance class 6az before coating per ISO 10684 for fit with 6H nuts. Class 10.9 and 12.9 require hydrogen embrittlement controls when electroplated.

Marking & Certification
Head permanently marked with standard number (DIN 961 or ISO 8676), property class (8.8, 10.9, or 12.9), and manufacturer’s identification mark. Full traceability maintained from mill certificate to shipment. EN 10204 Type 3.1 inspection certificates available on request. Go/No‑Go thread gauging performed on every batch.

Application Suitability
Automotive engine and drivetrain assemblies, hydraulic manifolds, high‑pressure fluid connections, precision machinery, and vibration‑loaded joints requiring fine adjustment and high clamp force. Fully threaded design is optimal for pre‑tapped blind holes and variable grip lengths. For shear‑critical joints where the unthreaded shank should intersect the shear plane, DIN 960 partial‑thread bolts are preferred.