Overview
EN ISO 8673:2023 (ISO 8673:2023) is the CEN-adopted international standard for hexagon regular nuts (style 1) with metric fine pitch thread. It specifies the characteristics, dimensions and requirements for steel and stainless‑steel hex nuts with fine pitch threads from 8 mm to 39 mm, covering product grades A and B. Nuts larger than 39 mm are addressed informatively in Annex A. The standard is intended for manufacturers, purchasers and quality/engineering teams working with fasteners.
Key topics and technical requirements
- Scope and sizes: Dimensions and tolerances for metric fine‑pitch nuts M8 to M39 (8 mm–39 mm). Annex A covers historical nuts D > 39 mm.
- Materials & mechanical properties:
- Steel nuts: mechanical properties and heat‑treatment (quenching/tempering where applicable) referenced to ISO 898‑2. Product grade assignment: typically grade A for D ≤ 16 mm and grade B for D > 16 mm (as specified).
- Stainless steel nuts: grades and property classes referenced to ISO 3506‑2 (common symbols A2, A4 and grades D4/D6 also referenced).
- Threads & tolerances: Metric fine pitch thread tolerance position 6H and thread form per ISO 965‑1.
- Dimensions & styling: Figures and tables define parameters (with and without washer‑face) and dimensional symbols per ISO 225.
- Surface condition & coatings: Acceptance of uncoated, electroplated coatings (ISO 4042) or zinc‑flake systems (ISO 10683); other finishes by agreement.
- Inspection & quality: Acceptance inspection and lot identification per ISO 3269 and ISO 1891‑4; surface discontinuities per ISO 6157‑2.
- Marking & labelling: Product marking follows ISO 898‑2 (steel) or ISO 3506‑2 (stainless steel); package labelling must include reference to ISO 8673, size D×P, material/grade, coating, lot number and quantity.
Applications and users
- Who uses it: fastener manufacturers, OEMs, procurement specialists, mechanical design engineers, quality assurance and maintenance teams.
- Typical applications: machine assembly, industrial equipment, automotive subassemblies, construction fixings and any application requiring standardized hexagon nuts with fine pitch metric threads where controlled dimensions, mechanical properties and traceability are required.
Related standards
EN ISO 8673:2023 provides the definitive dimensional, material and marking framework for standardized hexagon regular nuts (style 1) with fine pitch threads, enabling consistent manufacturing, procurement and quality control across industries.
