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MS21045L3 - Hexagon Self Locking Nut

MS21045L3 - Hexagon Self Locking Nut

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$ 1.88 $ 1.88

MS21045L3 – 10-32 Self-Locking Nut (Nyloc), Steel, 250°F

Available now on the Airparts.aero Marketplace.

Overview

The MS21045L3 is a lightweight, hexagon, self-locking nut manufactured to a precise Military Standard. It is the modern, improved successor to the legacy AN365 series fiber locknut and represents the industry standard for securing #10-32 UNF bolts (such as the AN3 series) in the vast majority of airframe applications. Its reliable self-locking capability is derived from a captive nylon collar that provides a consistent prevailing torque, preventing the nut from loosening under vibration.

Constructed from high-strength, cadmium-plated steel, this nut is designed for performance and reliability. Its most critical design parameter is its operational temperature limit of 250°F (121°C), as the integrity of the nylon locking element can be compromised at higher temperatures. For general-purpose fastening in ambient temperature locations, the MS21045L3 is the specified, airworthy choice.

Key Features

  • Nylon Insert Self-Locking: Features a captive nylon collar that grips the bolt threads, providing a consistent prevailing torque that offers excellent resistance to loosening from vibration.

  • 250°F Temperature Rating: Certified for use in the vast majority of airframe, interior, and systems applications where temperatures will not exceed 250°F (121°C).

  • Lightweight Hexagon Design: Manufactured to the MS21045 standard for a reduced height and weight profile compared to the legacy AN365 nut it replaces.

  • Cadmium-Plated Steel: The nut body is fabricated from high-strength steel and plated with cadmium per QQ-P-416 for durability and superior corrosion resistance.

  • Supersedes AN365 Nuts: The MS21045 is the modern, approved replacement for the older AN365 series nut in most applications, offering improved performance and reliability.

  • MS Standard Compliance: Guarantees adherence to precise dimensional tolerances, material composition, and locking torque performance.

Technical Specifications

  • Part Number: MS21045L3

  • Legacy Part Number: AN365-1032

  • Component Type: Self-Locking Hex Nut (Nylon Insert)

  • Governing Specification: MS21045 / NASM21045

  • Material: Steel, Cadmium Plated

  • Locking Element: Nylon Insert

  • Thread Specification: #10-32 UNF-3B

  • Maximum Operating Temperature: 250°F (121°C)

Aircraft Compatibility

The MS21045L3 is one of the most common pieces of hardware in aviation, used universally across all sectors where a #10-32 self-locking nut is required for ambient temperature applications.

  • Military Fighter, Transport, and Rotorcraft

  • Commercial and Transport Category Airliners (Boeing, Airbus)

  • Business and Corporate Jets (Textron Aviation, Bombardier, Gulfstream)

  • All General Aviation aircraft (Piston and Turbine)

Note: Verification of applicability is the responsibility of the installer. Always consult the current version of the aircraft's Illustrated Parts Catalog (IPC) and maintenance manual to confirm part number eligibility and the correct temperature rating for a specific location.

Applications

  • The standard locking nut for AN3-XXA series bolts.

  • Used for securing inspection panels, fairings, brackets, clamps, and systems hardware.

  • For assembly of interior components, avionics trays, and secondary structures.

  • Not for use in high-temperature areas such as firewall forward, engine compartments, or near bleed air ducts.

Why Choose MS21045L3?

Adherence to temperature limitations for hardware is a fundamental rule of aircraft maintenance. The MS21045L3 is the correct, specified fastener for the majority of airframe connections. Using a certified MS-spec nut ensures that the locking performance is reliable and the materials are traceable and correct. It prevents the catastrophic error of installing a nylon-insert nut in a high-temperature zone where an all-metal nut (like the MS21044N3) is required, which would lead to a complete loss of the self-locking feature.

The MS21045 specification represents a significant material science evolution from the legacy AN365 "fiber locknut" it supersedes. The older AN365 nuts used a compressed, vulcanized fiber insert, which was effective but prone to drying out, shrinking, and offering inconsistent prevailing torque over time and limited reusability. The MS21045L3 employs a modern, injection-molded nylon (polyamide) collar. This advanced polymer provides superior elasticity and "memory," allowing it to endure the elastic deformation of multiple bolt installations while maintaining a consistent and predictable prevailing torque. This results in a more reliable lock, a longer service life with more consistent reuse characteristics, and better resistance to hydraulic fluids and oils, making it a technically superior component for modern aircraft assembly and maintenance.

Note: This is a flight-critical hardware component. The 250°F (121°C) temperature limitation must be strictly observed. Installation must be performed by a certified mechanic using a calibrated torque wrench. This nut is reusable for a limited number of cycles; however, if it can be run down to the threads by hand, it has lost its locking capability and must be replaced. Always consult the maintenance manual for specific reuse criteria.

Documentation

The military standard governing this part is publicly available through the Department of Defense ASSIST database.