NAS1805-4 - Aerospace Self-Locking Nut

NAS1805-4 – Aerospace Self-Locking Nut

Available now on the Airparts.aero Marketplace.

Overview

The NAS1805-4 is a National Aerospace Standard, high-temperature, 12-point self-locking nut engineered for the most demanding structural applications in aviation and aerospace. This fastener is precision-machined from A-286 corrosion-resistant steel (CRES), a high-performance superalloy renowned for its exceptional strength retention at elevated temperatures. Featuring an extended washer base and a prevailing torque locking mechanism, the NAS1805-4 is designed for use on high-strength bolts in critical areas such as engine compartments, exhaust systems, and high-performance airframes where heat, vibration, and reliability are primary concerns. It has 12 drive points, 24 sides, and an integral washer that extends beyond the points or periphery. An integral feature is incorporated for locking on the threads of a mating member.

Key Features

• High-Temperature A-286 CRES Construction: Fabricated from A-286, an iron-nickel-chromium superalloy. This material provides excellent strength and creep resistance at temperatures up to 800°F (427°C) and superior corrosion resistance.
• 12-Point Double Hexagon Drive: The 12-point head design allows for higher torque application with reduced risk of wrench slippage compared to a standard 6-point hex nut. This enables proper preloading of high-strength bolts and provides multiple engagement angles in tight spaces.
• Prevailing Torque Self-Locking: Features an all-metal, deformed-thread locking mechanism. This provides a consistent, reusable locking action that is not dependent on a non-metallic insert, making it suitable for high-temperature environments where a nylon insert would fail.
• Extended Washer Base: The integral extended washer provides a broad, flat bearing surface. This distributes the high clamping force evenly, protecting the underlying structure (especially composites and aluminum) from damage and galling.
• NAS Certified Standard: Manufactured in strict accordance with the NAS1805 standard, guaranteeing material composition, heat treatment, dimensional tolerances, and locking performance for flight-critical applications.

Technical Specifications

• Standard: NAS1805
• Full Part Number: NAS1805-4
• Component Type: 12-Point, Extended Washer, Self-Locking Nut
• Material: A-286 Corrosion-Resistant Steel (CRES)
• Finish: Passivated (per QQ-P-35)
• Head Style: 12-Point Double Hexagon
• Thread Specification: 1/4-28 UNJF-3B
  • Nominal Diameter: 1/4 inch (0.250 inches)
  • Threads Per Inch: 28 (Fine Thread, with controlled root radius)
• Maximum Operating Temperature: 800°F (427°C)
• Wrench Size: 5/16 inch (12-point socket)

Aircraft Compatibility

The NAS1805-4 is a high-performance fastener specified for use in critical, high-temperature structural joints on a wide range of commercial, military, and high-performance general aviation aircraft. Its use is dictated by the manufacturer's engineering requirements for heat and strength.

• Common Applications:
  • Engine & Firewall Forward: Securing components on and around the engine, including exhaust system attachments, turbocharger installations, and firewall-mounted hardware.
  • Bleed Air Systems: Fastening components of high-temperature pneumatic bleed air ducts.
  • High-Performance Airframes: Used in structural joints of high-performance piston and turbine aircraft where standard AN nuts are insufficient.

Applications

The NAS1805-4 is the engineered solution for fastening challenges that exceed the capabilities of standard locknuts:

• High-Temperature Joints: Its primary application is in bolted joints that are exposed to significant heat, where it maintains its locking ability and tensile strength.
• High-Vibration & High-Tensile Loading: The combination of a 12-point head for high torque and an all-metal locking feature makes it ideal for securing joints under severe vibration and high tension loads.
• Critical Structural Connections: Used where the failure of a fastener due to temperature, vibration, or load would be catastrophic.

Why Choose NAS1805-4?

Standard AN self-locking nuts, especially those with nylon inserts (MS21044, AN365), cannot be used in high-temperature environments as the locking element will melt or degrade. The NAS1805-4 provides a robust, all-metal solution that maintains its integrity and locking performance in the hottest parts of an aircraft. Using a genuine NAS1805-4 nut ensures you are installing a fastener with the certified material properties and engineering design required to maintain a safe and airworthy connection in the most extreme conditions. For high-temperature structural applications, there is no substitute.

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Order Your NAS1805-4 Nuts Now

Secure your aircraft's most critical, high-temperature connections with certified aerospace hardware. Visit Airparts.aero to order your NAS1805-4 self-locking nuts today.

The NAS1805-4 utilizes a sophisticated all-metal, prevailing torque locking mechanism. The top portion of the nut's threads are subtly deformed into a non-circular or elliptical shape. When a bolt is threaded through, these deformed threads elastically grip the bolt, creating a strong frictional force that resists rotation. This locking action is effective from the first installation and is reusable for a specified number of cycles (typically around 15). The selection of A-286 CRES (UNS S66286) is critical; this precipitation-hardenable superalloy maintains its high tensile strength and resists creep and stress relaxation at temperatures where conventional stainless or alloy steels would lose their mechanical properties, ensuring the locking feature and clamp load remain effective even when heated.

Note: This is a flight-critical structural component. It must only be used where specified by the aircraft manufacturer's maintenance or structural repair manual. Installation requires the use of a calibrated torque wrench and a 12-point socket. Adherence to specified torque values is essential to achieve proper bolt preload.

Item Specification