Overview
ISO 7043:2012 specifies the characteristics of prevailing torque type hexagon nuts with flange (with non‑metallic insert), style 2, for metric threads M5 to M20. It covers dimensional limits, product grades (A for D ≤ M16, B for D > M16), and property classes 8, 9 and 10. The standard defines how these self‑locking flange nuts (with a non‑metallic insert such as polyamide) should be produced and inspected to ensure fit, function and compatibility with metric threaded fasteners.
Key topics and technical requirements
- Scope and thread range: Threads M5–M20 inclusive; product grade A (up to M16) and B (above M16); property classes 8, 9, 10.
- Dimensions: Nut geometry is based on ISO 4161 (hexagon nuts with flange, style 2) with added prevailing‑torque features; detailed dimensional tables (e.g., flats, wrenching height, flange thickness) are provided.
- Materials and insert: Nut body - steel; insert example - polyamide (non‑metallic). Specific materials/coatings must meet referenced standards.
- Threads and tolerances: Tolerance class 6H for internal threads; general thread forms per ISO 261/ISO 724 and limits per ISO 965‑2.
- Mechanical and performance properties: Referenced to ISO 898‑2 and ISO 2320 for mechanical characteristics and prevailing torque behavior.
- Surface finish and coatings: Electroplated coatings per ISO 4042; non‑electrolytically applied zinc‑flake coatings per ISO 10683; other finishes by agreement.
- Quality and acceptability: Surface discontinuities per ISO 6157‑2; acceptance inspection per ISO 3269.
- Gauging: Annex A describes practical gauging using three ring/feeler gauges (A, B, C) to verify hexagon height, wrenching height, corner fill and flange thickness.
Applications and who uses it
ISO 7043:2012 is used by:
- Manufacturers of self‑locking flange nuts to design and produce prevailing torque hexagon nuts that meet international tolerances and performance classes.
- Procurement and quality engineers specifying fasteners for assemblies requiring vibration‑resistant locking behavior (automotive, machinery, construction, and general engineering).
- Test and inspection labs performing dimensional gauging and acceptance inspection of locking nuts.
- Designers and maintenance engineers selecting compliant fasteners for safety‑critical joints where consistent locking torque is required.
Related standards
Keywords: ISO 7043:2012, prevailing torque hexagon nuts, hexagon nuts with flange, non‑metallic insert, product grade A, product grade B, M5 to M20, property class 8 9 10, fastening standard, fastener gauging.
Open preview (PDF)Prevailing torque type hexagon nuts with flange (with non-metallic insert), style 2 — Product grades A and B