Overview
ISO 8674:2023 specifies the characteristics of hexagon high nuts (style 2) with metric fine pitch thread for sizes 8 mm to 39 mm, in both steel and stainless steel, and with product grades A and B. The fourth edition (2023) updates dimensions, adds several fine-pitch sizes (e.g., M18×2, M20×2, M22×2, M39×3), and includes stainless-steel options, marking and labelling rules, and tightened material/heat-treatment references. Nuts are normally delivered without a washer-face unless otherwise ordered.
Key topics and technical requirements
- Thread sizes and pitches: Metric fine pitch threads from M8 to M39 are covered; dimensional details are given in Figures and Tables for product grades A (smaller sizes) and B (larger sizes).
- Material and mechanical properties:
- Steel nuts: property classes (e.g., 8, 10, 12) referenced to ISO 898-2; quenching and tempering requirements specified where applicable.
- Stainless steel: common grades such as A2, A4, D4, D6 and property classes (e.g., A4-80) referenced to ISO 3506-2.
- Tolerances and thread fit: Thread tolerance class 6H and general thread tolerancing per ISO 965-1.
- Surface condition and coatings: Default delivery - steel “as processed” and stainless steel “clean and bright” unless coatings/finishes are specified. Electroplated (ISO 4042) and zinc-flake (ISO 10683) coatings and passivation (e.g., ISO 16048) are covered for agreed requirements.
- Dimensional details: Optional washer-face, tolerances, hex sizes, heights and other geometrical parameters are defined in the standard’s tables and figures.
- Marking, labelling and designation:
- Product marking follows ISO 898-2 (steel) or ISO 3506-2 (stainless steel).
- Package labelling must include ISO reference (ISO 8674), thread size D×P, property class/grade, surface finish, manufacturer ID, lot number and quantity.
- Designation examples are provided (e.g., “Hexagon high nut ISO 8674 – M24×2 – 10”).
Applications and users
ISO 8674 is intended for manufacturers, fastener distributors, procurement specialists, mechanical designers and quality inspectors who require standardized hexagon high nuts with fine pitch threads for:
- Automotive, machinery and heavy equipment assemblies where fine-pitch clamping is needed
- High-precision or high-load bolted joints requiring controlled thread engagement
- Corrosion-resistant applications using stainless-steel grades and specified surface treatments
- Supply chain and procurement to ensure consistent marking, labelling and acceptance inspection
Related standards
Relevant standards referenced by ISO 8674 include:
Keywords: ISO 8674, hexagon high nuts, fine pitch thread, metric fine pitch, product grade A, product grade B, stainless steel nuts, ISO 898-2, ISO 3506-2.
