Overview
ISO 3224:1998 is an aerospace product standard that specifies the dimensions for a specific class of nuts: self‑locking, floating, single‑lug anchor nuts with counterbore and MJ threads. It covers nuts of the classifications 1 100 MPa (at ambient temperature)/235 °C, 1 100 MPa/315 °C and 1 100 MPa/425 °C. The standard is intended for the compilation of aerospace product standards and ensures dimensional interchangeability and compatibility with related procurement specifications.
Key topics and requirements
- Part geometry and dimensions: Detailed configuration, dimension tables and figure references define external and internal dimensions expressed in millimetres.
- Threading: Applies to MJ threaded anchor nuts; limits and thread dimensions follow the MJ system referenced in ISO 5855‑2.
- Self‑locking and floating features: Specifies dimensions for the self‑locking zone and single‑lug floating configuration that allow for controlled movement and locking performance.
- Temperature classifications: Defines three maximum operating temperature classes (235 °C, 315 °C, 425 °C) tied to material/treatment and intended performance after exposure.
- Surface and assembly conditions: Dimensions apply after any surface coating(s) but before application of lubricant; the optional metallic cap must remain attached at maximum operating temperature (test conditions per ISO 5858).
- Tolerances and form: Tolerances of form and position are governed by ISO 8788; specific manufacturing details not stated are left to manufacturer discretion.
- Normative references: Includes ISO 5855‑2 (MJ threads limits), ISO 5858 (procurement specification for self‑locking nuts), and ISO 8788 (tolerances for nuts).
Applications and users
ISO 3224 is primarily used by:
- Aerospace fastener designers and engineers specifying anchor nuts for airframe and engine components.
- Manufacturers producing self‑locking, floating, single‑lug anchor nuts to ensure dimensional conformity.
- Procurement and quality assurance teams verifying parts against aerospace product standards.
- Maintenance and repair organizations selecting replacement fasteners compatible with MJ threads and high‑temperature service.
Practical uses include panel attachment systems, bracket and lug assemblies where misalignment accommodation (floating lug) and secure locking at elevated temperatures are required.
Related standards
- ISO 5855‑2: MJ threads - limit dimensions for bolts and nuts.
- ISO 5858: Self‑locking nuts with maximum operating temperature ≤ 425 °C - procurement specification.
- ISO 8788: Fasteners - tolerances of form and position for nuts.
Keywords: ISO 3224, aerospace nuts, anchor nuts, self‑locking, floating single‑lug, MJ threads, dimensions, high‑temperature classification, aerospace fastener standards.