EN 4673-002:2010

Overview

EN 4673-002:2010 is a European standard under the Aerospace series developed by CEN, specifying the design requirements for inserts featuring UNJ threads that are self-locking and equipped with self-broaching keys. These inserts are intended primarily for aerospace applications, providing detailed guidance on installation hole dimensions, applications, and provisions for component salvage in aerospace components.

The standard ensures compatibility with UNJ threaded bolts per ISO 3161 and defines performance and installation criteria to maintain mechanical integrity and durability critical in aerospace environments.

Key Topics

• Design Specifications
  Defines installation hole dimensions, flange thickness requirements, and tool clearance considerations specific to self-locking, self-broaching key UNJ threaded inserts. Includes codified hole dimensions for normal and repair sizes, enabling standardized component design and repair processes.

• Self-Locking Mechanism
  Inserts include self-broaching keys that cut into the parent thread during installation to secure the insert, preventing movement during bolt mounting/unmounting. The self-locking feature operates independently from the key side, ensuring reliable fixation.

• Performance Requirements
  Ensures minimum reusability of the inserts: at least 25 re-installations at ambient temperature and 5 cycles post high-temperature baking, with specified self-locking torque parameters aligned with insert size.

• Installation and Use Restrictions
  Specifies tolerances for flush or near-flush insert installation within components (0.25 mm to 0.75 mm below surface), including maximum allowable clearance diameters for items passed through the inserts. It also defines limitations to avoid interference during assembly.

• Component Salvage Provisions
  Provides guidance for repair scenarios, encouraging salvage practices for expensive aerospace parts through recommended hole preparation and selection of repair-size inserts. Addresses economic considerations of salvage versus replacement.

• Designation and Drawing Standards
  Outlines naming conventions for inserts based on diameter and repair size, and presents recommended methods for indicating installation holes on technical drawings, including codification and full dimensioning methods.

Applications

The EN 4673-002:2010 standard is essential for aerospace engineers, designers, and manufacturers working with threaded inserts in:

• Aircraft structural components
  Where high-strength, reusable threaded connections are required under demanding load and temperature conditions.

• Engine assemblies and mounting points
  Supporting reliable bolt retention and ease of component repair through standardized insert dimensions and installation protocols.

• Aerospace repair and maintenance
  Facilitating component salvage via defined repair insert sizes and installation practices, reducing costs associated with component replacement.

• Lightweight alloys and high-performance materials
  Including aluminum, titanium, and heat-resistant steels, where thread reinforcements via inserts prolong service life and improve reliability.

Related Standards

• EN 4673-001: Installation and removal procedure
  Covers step-by-step instructions for installing and removing inserts defined in EN 4673 series.

• EN 4673-003: Technical specification
  Details the technical requirements and tolerances concerning the inserts’ manufacture and performance.

• ISO 3161: Aerospace – UNJ threads – General requirements
  Specifies general dimensions and limits for UNJ threads, ensuring compatibility across aerospace threaded components.

Keywords: aerospace threaded inserts, UNJ threads, self-locking inserts, self-broaching keys, aerospace fasteners, aerospace repair inserts, aerospace design standards, EN 4673-002, aerospace component salvage, bolt thread inserts, CEN aerospace standards.