SIST EN ISO 7042:2025 PDF

Overview

EN ISO 7042:2025 - Fasteners: Prevailing torque hexagon high nuts (all metal) specifies the characteristics of all‑metal prevailing‑torque hexagon high nuts in steel and stainless steel, for metric coarse‑pitch threads M5 to M39, and for product grades A and B. The standard defines dimensions, tolerances, functional requirements and marking/labelling rules for these locking (prevailing torque) nuts as endorsed by CEN (European adoption of ISO 7042:2025).

Key topics and technical requirements

• Scope and design: Covers hexagon high nuts with an integrated prevailing‑torque feature (shape at manufacturer’s discretion within the hex outside profile). Overall height hmin = mmin (style 2 base) plus the prevailing torque feature; hmax is set relative to hmin and does not follow the ISO IT tolerance code. Wrenching height corresponds to style 1.
• Size range and dimensions: Thread sizes from M5 to M39 (tables and figures specify a, d, h, s, w and other dimensions). Some new sizes (e.g., M7, M18, M22, M27, M33, M39) are included in this edition.
• Materials and grades:
  • Steel nuts: property classes per ISO 898‑2; quenching/tempering and NQT/QT options as referenced.
  • Stainless steel nuts: grades and property classes per ISO 3506‑2 (common grades A2, A4 listed; other grades selectable as required).
• Product grades: Grade A for D ≤ M16 (with special note for M5 thread bearing area); grade B for D > M16.
• Threads and tolerances: Default thread tolerance class 6H; 6G may be specified for coated nuts. Thread standard is ISO 965‑1.
• Functional tests and coatings: Functional properties for steel nuts reference ISO 2320. Surface finishes, electroplated coatings and zinc‑flake systems reference ISO 4042 and ISO 10683. Surface discontinuities and acceptance use ISO 6157‑2 and ISO 3269.
• Marking & labelling: Clause added specifying marking on product and labelling on packaging (steel marking follows ISO 898‑2).

Applications and users

• Practical uses: selection and specification of all‑metal prevailing‑torque hexagon high nuts for mechanical assemblies requiring vibration resistance and secure locking where a metal‑on‑metal prevailing feature is preferred.
• Who uses this standard:
  • Fastener manufacturers and designers
  • Mechanical/assembly engineers and procurement specialists
  • Quality, testing and inspection teams
  • Standards bodies and compliance teams in industry sectors using metric fasteners

Related standards (selection)

• ISO 898‑2 - mechanical properties of nuts (steel)
• ISO 3506‑2 - stainless steel nuts
• ISO 2320 - prevailing torque steel nuts (functional properties)
• ISO 965‑1, ISO 4759‑1, ISO 4042, ISO 10683, ISO 3269, ISO 6157‑2

EN ISO 7042:2025 is essential when specifying metric prevailing‑torque high hex nuts (M5–M39) to ensure dimensional compatibility, mechanical performance and conformity with European/ISO fastener practice.