Overview
ISO 7040:2012 defines the characteristics of prevailing torque type hexagon regular nuts (with non‑metallic insert). It covers metric threads from M3 to M36, in property classes 5, 8 and 10, and specifies product grade A for threads up to M16 and grade B for threads above M16. Dimensions correspond to ISO 4032 plus the locking (insert) system.
Keywords: ISO 7040, prevailing torque nuts, hexagon regular nuts, non‑metallic insert, nylon insert nuts, property class 5 8 10, metric threads M3–M36.
Key topics and requirements
- Scope: Prevailing‑torque hexagon regular nuts with a non‑metallic insert (e.g., polyamide as an example material for the ring) for threads M3–M36.
- Property classes: 5, 8 and 10 - mechanical performance categories referenced to ISO 898‑2 and ISO 2320 where applicable.
- Product grades: Grade A for D ≤ M16, Grade B for D > M16 (tolerances described in ISO 4759‑1).
- Thread tolerance: 6H for internal threads.
- Dimensions: Follow ISO 4032 as the baseline; ISO 7040 adds the locking‑ring geometry (see figure and table in the standard).
- Materials and surface finishes: Nut body typically steel; insert examples include polyamide. Coating and finish requirements are referenced to ISO 4042 (electrolytic) and ISO 10683 (non‑electrolytic zinc flake).
- Inspection and acceptance: Reception and sampling per ISO 3269; surface defect limits per ISO 6157‑2.
- Designation example: “Hexagon regular prevailing‑torque nut ISO 7040 - M12 - 8”
Applications and users
Practical uses of ISO 7040 prevailing‑torque nuts include assemblies requiring vibration resistance and reusable locking (where a non‑metallic insert provides prevailing torque). Typical sectors and users:
- Fastener and component manufacturers specifying production dimensions and tolerances
- Design and mechanical engineers selecting locking nuts for machinery, automotive, rail, construction and industrial equipment
- Procurement professionals ensuring compliance with specified property classes and grades
- Quality and inspection teams performing acceptance checks and surface/coating verification
- Maintenance teams choosing compatible replacement fasteners with predictable locking performance
Related standards
ISO 7040 cross‑references and complements several ISO documents:
Use ISO 7040:2012 when you need standardized prevailing‑torque hexagon nuts with a non‑metallic insert and clear rules for dimensions, tolerances, material references and inspection - ensuring interchangeability and consistent locking performance across designs.
Open preview (PDF)Prevailing torque type hexagon regular nuts (with non-metallic insert) — Property classes 5, 8 and 10