ISO 12273:2010

Overview

ISO 12273:2010 specifies the dimensions of aerospace anchor nuts: floating, self-aligning, two-lug, with MJ threads and a self‑locking feature. The standard covers nuts classified for 900 MPa tensile capability (at ambient temperature) with maximum exposure temperatures of 235 °C, 315 °C and 425 °C. It is intended for use in the compilation of aerospace product standards and provides the dimensional definitions, tolerances and configuration information necessary for design, procurement and manufacture of these specialized fasteners.

Key topics and technical requirements

• Scope of coverage: Floating, self-aligning, two-lug anchor nuts with MJ threads and self-locking achieved by forming the upper portion out‑of‑round. Applicable classifications: 900 MPa/235 °C, 900 MPa/315 °C, 900 MPa/425 °C.
• Dimensional data: Complete figures and tabulated dimensions (in millimetres) are provided for relevant MJ thread sizes. Dimensions apply after any surface coating(s) but before lubrication.
• Tolerances and form: Tolerances of form and position conform to ISO 8788. Thread limit dimensions reference ISO 5855‑2. In the self‑locking zone, tolerances apply before forming out‑of‑round.
• Functional notes: The document clarifies that the first element of a classification (900 MPa) is the minimum tensile stress the nut withstands at ambient temperature when tested with a higher-strength bolt; the second element is the maximum temperature the nut can endure without permanent alteration after returning to ambient.
• Performance features: Requirements include radial float and axial misalignment allowances (e.g., a minimum axial misalignment around the central position is specified in the standard) and self‑locking torque achieved by controlled out‑of‑round forming.

Applications and users

• Who uses ISO 12273:2010: Aerospace design engineers, fastener manufacturers, quality assurance and inspection teams, procurement/specification writers, and standards committees compiling aerospace product standards.
• Practical uses: Ensures interchangeability and reliable performance of aerospace nuts, supports procurement specifications, guides tooling and manufacture of anchor nuts with MJ threads, and helps maintain high‑temperature and high‑strength fastener integrity in airframe and engine applications.
• Value: Reduces design ambiguity, ensures conformity across suppliers, and links mechanical dimensions to classification requirements (strength and temperature).

Related standards

• ISO 5855‑2 - MJ threads: limit dimensions for bolts and nuts (referenced for thread limits)
• ISO 8788 - Nuts, metric: tolerances of form and position
• ISO 5858 - Procurement specification for self‑locking nuts with maximum operating temperature ≤ 425 °C

Keywords: ISO 12273:2010, aerospace nuts, anchor nuts, MJ threads, self-locking, floating self-aligning two-lug anchor nuts, dimensions, 900 MPa, high-temperature fasteners, aerospace fastener standards.