ISO 12274:1997

Overview

ISO 12274:1997 specifies the dimensions for a specialized class of aerospace nuts: anchor, self-locking, floating, self-aligning, single-lug nuts with MJ threads, rated at a tensile classification of 900 MPa for ambient temperature and qualified for maximum exposure temperatures of 235 °C, 315 °C, and 425 °C. Prepared by ISO/TC 20 (Aircraft and space vehicles) SC 4 (Aerospace fastener systems), the standard provides dimensional requirements used when compiling aerospace product standards.

Key topics and technical requirements

• Product scope: Floating, self-aligning, single-lug anchor nuts with an integral self-locking feature achieved by forming the upper portion out-of-round.
• Classifications: Designated for nuts of 900 MPa minimum tensile stress at ambient temperature with maximum service-temperature categories of 235 °C, 315 °C, and 425 °C.
• Dimensions and tolerances:
  • Dimensions are given in millimetres and presented in figure(s) and table(s).
  • Tolerances of form and position must conform to ISO 8788 (Aerospace - Fasteners - Tolerances of form and position for nuts).
  • Surface texture tolerances apply before coating(s) and before lubricant application.
• Self-locking method: Locking is achieved by intentional out-of-round forming in the self-locking zone; tooling marks in this area are permissible.
• Floating/self-aligning features: The design accommodates axial misalignment (minimum deflection noted in the standard) to enable alignment during assembly.
• Reference and conformity: Dimensions were determined to satisfy the procurement specification of ISO 5858, and the standard references ISO 5855-2 and ISO 5858:1991 among others.

Applications and users

This standard is intended for use in the aerospace industry where high-strength, temperature-capable, self-locking anchor nuts are required. Typical users include:

• Aerospace design and structural engineers specifying fasteners for airframe components.
• Fastener manufacturers and quality control teams producing or inspecting MJ-thread anchor nuts.
• Procurement/specification writers compiling aerospace product standards and purchase documents.
• Maintenance and assembly engineers needing standardized, interchangeable anchor nuts for repair or retrofit.

Practical applications include attachment points where a floating, self-aligning nut with high tensile capacity and elevated temperature resistance is required (e.g., engine mounts, hot-structure assemblies, or other critical airframe joints).

Related standards

• ISO 5855-2 - MJ threads, limit dimensions for bolts and nuts (referenced)
• ISO 5858:1991 - Aerospace - Self-locking nuts procurement specification (referenced)
• ISO 8788:1987 - Fasteners - Tolerances of form and position for nuts (referenced)

Keywords: ISO 12274:1997, aerospace nuts, anchor nuts, self-locking, floating nuts, MJ threads, dimensions, 900 MPa, aerospace fasteners.