Overview - EN ISO 7719:2025 (Prevailing torque hexagon nuts)
EN ISO 7719:2025 specifies the characteristics of prevailing torque (all‑metal) hexagon regular nuts manufactured in steel and stainless steel, covering metric coarse‑pitch threads M5 to M39 and product grades A and B. The standard defines dimensional requirements, material and mechanical references, tolerances, surface condition options, and marking/labelling rules for these fasteners. It clarifies design principles (including a specific note on nut height tolerances) and updates sizes and material options from earlier editions.
Key topics and technical requirements
- Scope and sizes: Applies to hexagon regular nuts with prevailing‑torque feature, thread sizes M5–M39 and product grades A (smaller sizes) and B (larger sizes).
- Materials: Steel and stainless‑steel options are included; property classes and stainless grades are referenced to ISO 898‑2 and ISO 3506‑2 respectively.
- Dimensions: Detailed dimensions for M5–M16 (Table 1) and M18–M39 (Table 2) with symbols and limits derived from ISO 225. The prevailing‑torque feature shape is at manufacturer’s discretion within the hex profile.
- Height/tolerance note: Nuts are designed with overall height hmin = mmin (as per ISO 898‑2 / ISO 4032 style 1) plus the prevailing‑torque feature; hmax is established relative to hmin, so (hmax − hmin) does not follow the ISO IT tolerance system.
- Threads and tolerances: Thread tolerance class 6H (or 6G for coated parts where specified) and general thread requirements per ISO 965‑1.
- Functional & acceptance criteria: Functional properties and testing are linked to ISO 2320 and other referenced standards; acceptance inspection follows ISO 3269.
- Surface and coatings: Options include clean/bright, electroplated (ISO 4042), non‑electrolytic zinc‑flake (ISO 10683), passivation and lubrication - additional finishes by agreement.
- Marking & labelling: Clause 6 specifies product marking and package labelling requirements.
Applications and who uses the standard
- Manufacturers and designers of fasteners who need consistent dimensions and functional characteristics for prevailing‑torque hex nuts.
- Quality, procurement and inspection teams specifying compliant nuts for machinery, automotive, construction, industrial equipment and maintenance.
- OEMs and suppliers requiring interoperable fasteners with defined mechanical properties and traceability.
- Standards bodies and labs referencing consistent test and acceptance criteria for production and conformity.
Related standards (for specification and compliance)
Keywords: EN ISO 7719:2025, prevailing torque hexagon nuts, all‑metal nuts, fasteners, M5–M39, product grades A and B, ISO 7719.
