ISO 3168:1998

Overview

ISO 3168:1998 is an international standard developed by ISO to specify the dimensional requirements for aerospace anchor nuts. Specifically, this standard details the dimensions of self-locking, fixed, single lug anchor nuts with counterbore and MJ threads. These nuts are designed to meet classifications defined by their tensile strength of 1,100 MPa at ambient temperature and their maximum operating temperatures of 235°C, 315°C, or 425°C.

Intended for reference in the development and compilation of other aerospace product standards, ISO 3168:1998 supports manufacturers, engineers, and procurement professionals in the aviation and space sectors who require reliable and interchangeable fastening components that meet rigorous performance criteria.

Key Topics

• Anchor Nut Specifications: Focuses on anchor nuts that are self-locking, fixed, single lug type, and counterbored with MJ threads, which are widely used in aerospace assemblies for their strength and vibration-resistance properties.
• Classification:
  • 1 100 MPa (at ambient temperature) / 235°C
  • 1 100 MPa (at ambient temperature) / 315°C
  • 1 100 MPa (at ambient temperature) / 425°C
• Dimensional Requirements: Prescribes detailed metric dimensions and tolerances for these nuts, ensuring compatibility and interchangeability within aerospace systems.
• Conformance with Related Standards: References ISO 5855-2 for thread specifications, ISO 5858 for procurement, and ISO 8788 for tolerances of form and position.
• Application Context: For use exclusively in the compilation of aerospace product standards, supporting uniformity and performance in critical fastening applications.

Applications

The anchor nuts defined in ISO 3168:1998 are essential fastening solutions in aerospace assemblies. Their robust design and self-locking feature serve several practical purposes:

• Aircraft Assembly: Used in securing structural components, access panels, and systems where reliable locking of fasteners is critical for safety and longevity.
• Spacecraft Components: Preferred in situations where vibration resistance and the ability to withstand high operational temperatures are vital.
• Maintenance and Repair: Standardized dimensions allow for easier replacement and sourcing during ongoing maintenance cycles of aircraft and aerospace vehicles.
• Aerospace Fastener Standardization: Enables manufacturers and engineers to specify and source compatible anchor nuts from different suppliers, simplifying supply chains and ensuring quality across international projects.

Related Standards

ISO 3168:1998 builds upon and complements several other key aerospace fastener standards:

• ISO 5855-2:1988 - Aerospace - MJ threads - Limit dimensions for bolts and nuts.
• ISO 5858:1991 - Aerospace - Self-locking nuts with maximum operating temperature ≤425°C - Procurement specification.
• ISO 8788:1987 - Aerospace - Fasteners - Tolerances of form and position for nuts.

Keywords: ISO 3168, aerospace anchor nuts, self-locking nuts, single lug, MJ threads, counterbore, fastener standards, aircraft fasteners, space vehicle components, aerospace standards, nut dimensions, high-temperature fasteners, international standardization.