EN 4117:2004

Overview

EN 4117:2004 is a European Standard developed by CEN for aerospace applications, specifying the characteristics of self-locking bihexagonal nuts made from heat resisting nickel base alloy NI-PH2601 (Inconel 718), with a silver-plated thread. This standard covers nuts classified for use up to 1,550 MPa tensile strength at ambient temperature and service temperatures up to 600 °C, making them suitable for demanding aerospace environments. The document addresses configuration, material requirements, surface treatment, marking, and technical specifications for these specialized fasteners.

Key Topics

• Material Specification: Defines nuts manufactured from NI-PH2601 (Inconel 718), a nickel base alloy known for its heat and corrosion resistance.
• Self-Locking Feature: Outlines self-locking mechanisms achieved by out-of-round forming, ensuring vibration resistance and secure fastening in critical applications.
• Bihexagonal Design: Details the twelve-point (bihexagonal) configuration for enhanced wrenching and torque application, complying with ISO 4095.
• Thread and Plating: Specifies the use of MJ metric series threads (per ISO 5855-2) with silver plating applied to threads and chamfers to improve galling resistance and anti-seize properties.
• High Strength Classification: Nuts are rated at a minimum 1,550 MPa tensile strength at room temperature and can operate in environments up to 600 °C.
• Dimensional and Marking Requirements: Provides dimensional tolerances and mandatory marking practices in accordance with EN 2424 for aerospace identifiability and traceability.

Applications

EN 4117:2004 is widely applicable in aerospace engineering, particularly in situations demanding high strength, elevated temperature resistance, and reliable locking performance. Typical use cases include:

• Aircraft Structures: Fastening of critical structural elements where high mechanical loads and temperature resistance are required.
• Aerospace Engines: Components subjected to extreme thermal cycles, vibration, and environmental stress.
• Spacecraft and Satellite Assemblies: Hardware requiring long-term stability and resistance to loosening in harsh, vibration-prone environments.
• Other High-Performance Environments: Situations outside aerospace, such as high-performance automotive or energy sectors, where similar demanding criteria for fasteners exist.

The combination of self-locking capability, bihexagonal design, and robust nickel alloy construction ensures reliability in safety-critical aerospace systems.

Related Standards

EN 4117:2004 references and aligns with several international and European standards to ensure compatibility and reliability across aerospace applications. Key related standards include:

• ISO 4095: Aerospace - Bihexagonal drives - Wrenching configuration - Metric series.
• ISO 5855-2: Aerospace - MJ threads - Part 2: Limit dimensions for bolts and nuts.
• EN 2424: Aerospace series - Marking of aerospace products.
• EN 2786: Aerospace series - Electrolytic silver plating of fasteners.
• EN 2952: Aerospace series - Heat resisting alloy NI-PH2601 - Solution treated and cold worked - Bar for forged fasteners.
• EN 4047: Aerospace series - Nuts, self-locking, MJ threads, in heat resisting nickel base alloy NI-PH2601 (Inconel 718), silver plated.

These standards together ensure comprehensive quality, compatibility, and traceability for aerospace fasteners, supporting the rigorous safety and performance demands of the industry.

Keywords: EN 4117:2004, aerospace nuts, bihexagonal self-locking nuts, NI-PH2601, Inconel 718, silver plated thread, high temperature fasteners, aerospace fastener standards, CEN, high strength nuts, self-locking nuts, aerospace hardware standardization.