Overview
EN ISO 7041:2025 - Fasteners: Prevailing torque hexagon high nuts (with non‑metallic insert) specifies the characteristics, dimensions and requirements for prevailing‑torque hexagon high nuts fitted with a non‑metallic insert (e.g., polyamide). It covers steel and stainless‑steel nuts with metric coarse pitch threads from M5 to M39, and defines product grades A and B. The standard ensures consistent mechanical and functional properties for self‑locking hexagon nuts used where vibration‑resistant fastening is required.
Key topics and technical requirements
- Scope and design: Overall nut height equals mmin (as per ISO 898‑2 / ISO 4033 for style 2) plus the prevailing‑torque feature; the insert height (hmax − mmin) is identical across regular, high and thin nuts for a given diameter.
- Sizes and dimensions: Detailed dimensions and tolerances are provided in Tables 1 and 2 (M5–M16 for product grade A; M18–M39 for product grade B) and Figure 1.
- Materials: Steel and stainless steel (common grades referenced in ISO 3506‑2). Insert material examples include polyamide.
- Mechanical and functional properties: Reference to ISO 898‑2 (mechanical properties for steel nuts) and ISO 3506‑2 (stainless steel); functional properties referenced to ISO 2320.
- Threads and tolerances: Thread tolerance class 6H (6G may be specified for coated nuts); general metric thread rules in ISO 965‑1 and ISO 225.
- Surface, coatings and finish: Guidance for electroplated (ISO 4042), zinc‑flake (ISO 10683), and acceptance/inspections (ISO 3269, ISO 6157‑2).
- Product grades & testing: Product grades A/B, tolerances per ISO 4759‑1; marking and labelling requirements are specified in Clause 6.
Applications and who uses it
- Applications: Specifying self‑locking hexagon high nuts for assemblies that require resistance to loosening under vibration and dynamic loads - common in machinery, automotive components, industrial equipment and general engineering assemblies.
- Users:
- Fastener manufacturers and designers (to design and produce nuts to uniform dimensions and properties)
- OEM engineers and procurement teams (for component specification and sourcing)
- Quality, inspection and testing laboratories (acceptance inspection and conformity checks)
- Standards specialists and regulatory bodies
Related standards
Keywords: EN ISO 7041:2025, prevailing torque hexagon nuts, non‑metallic insert, polyamide insert, M5–M39, product grades A and B, fastener standards, locking nuts.