MS21042L5 - Textron Aviation OEM Self-Locking Extended Washer Hex Nut

MS21042L5 – Textron Aviation OEM Self-Locking Extended Washer Hex Nut

Available now on the Airparts.aero Marketplace.

Overview

The MS21042L5 is a military-standard, lightweight, all-metal, self-locking hexagon nut, specified by Textron Aviation for use in aerospace applications where temperatures exceed the limits of common nylon insert locknuts. This fastener is engineered to provide a reliable, vibration-resistant locking action in moderately high-temperature environments up to 450°F (232°C). Manufactured from high-strength, cadmium-plated steel, the MS21042L5 utilizes a deformed-thread design to achieve its prevailing torque, making it a critical piece of hardware for firewall-forward and other demanding airframe applications on Cessna and Beechcraft aircraft.

Key Features

• All-Metal Locking Design: Features a precision-deformed elliptical thread at the top of the nut. This all-metal locking mechanism creates a powerful spring-like frictional grip on the bolt threads, providing a consistent prevailing torque that is resistant to high temperatures and vibration.
• 450°F Temperature Rating: The absence of a non-metallic insert allows this nut to maintain its structural and locking integrity at temperatures up to 450°F, making it the standard choice for numerous engine compartment applications where nylon insert nuts would fail.
• Lightweight Profile: Designed as a lightweight hex nut, offering an excellent strength-to-weight ratio, which is a key consideration in aerospace design where every gram is accounted for.
• High-Strength Steel Construction: Fabricated from a high-quality carbon steel alloy and heat-treated to provide the tensile strength required to properly preload standard AN structural bolts.
• MS Certified Standard: As a certified Military Standard part, it guarantees the material, dimensions, heat treatment, and locking torque performance meet the stringent requirements for use in certified aircraft. It is the superseding part for the legacy AN364-524 nut.

Technical Specifications

• Standard: MS21042 (Nut, Self-Locking, Hexagon, Lightweight, 450°F)
  

• Full Part Number: MS21042L5
• Legacy Part Number: AN364-524
• Component Type: All-Metal Prevailing Torque Self-Locking Nut
  
• Material (L): Carbon Steel
• Finish: Cadmium Plated
  
• Thread Specification: 5/16-24 UNJF-3B
  
  • Nominal Diameter: 5/16 inch (0.312 inches)
  • Threads Per Inch: 24 (Fine Thread)
    
• Wrench Size: 1/2 inch
• Maximum Operating Temperature: 450°F (232°C)
  

Aircraft Compatibility

The MS21042L5 is a universal hardware component used across all categories of aircraft, including numerous models from Textron Aviation, where a high-temperature, all-metal locknut is required for a 5/16" bolt.

• Common Textron Aviation Platforms:
  • Cessna: 182, 206, 210, 310, 421, Citation Series
  • Beechcraft: Bonanza, Baron, King Air Series
• Common Applications:
  • Firewall Forward: The primary application is for securing components in the engine compartment, such as engine baffles, accessories, brackets, and exhaust system heat shields.
  • Brake Systems: Used in close proximity to brake assemblies where high temperatures are generated.

Applications

The MS21042L5 is the specified fastener for creating secure joints in elevated temperature zones:

• Heat-Resistant Fastening: Provides a reliable, vibration-proof connection in areas that are too hot for standard AN365 / MS21044 nyloc nuts.
• Serviceable Joints: The all-metal design allows for reuse a limited number of times, provided the prevailing torque remains within the minimum specified limits.

Why Choose MS21042L5?

A standard nylon insert locknut will fail if its 250°F temperature limit is exceeded, resulting in a complete loss of the locking feature. The MS21042L5 provides the next level of thermal protection, ensuring fasteners remain secure in the hot, demanding environment of the engine compartment. Using a genuine MS-standard nut as specified by Textron Aviation guarantees that the part has the certified material properties and precisely engineered locking feature required for a safe and airworthy installation.

Website Metadata

• Meta Title: MS21042L5 All-Metal Self-Locking Nut, 5/16-24, 450°F | Textron OEM | Airparts.aero
  

• Meta Description: Purchase genuine MS21042L5 (AN364-524) military-standard self-locking nuts. This 5/16-24 all-metal locknut is rated to 450°F and specified by Textron Aviation for high-temperature applications.
  

• SEO and Plain Text Keywords: MS21042L5, self-locking nut, locknut, all-metal locknut, AN364-524, aircraft hardware, military standard hardware, 5/16-24 nut, high-temperature nut, Textron Aviation parts, Cessna parts, Beechcraft parts, Airparts.aero.

Order Your MS21042L5 Nuts Now

Secure your aircraft's high-temperature connections with certified, flight-critical hardware. Visit Airparts.aero to order your MS21042L5 all-metal self-locking nuts today.

SEO-Enhanced Addendum

The locking mechanism of the MS21042L5 is achieved through controlled thread deformation. During manufacturing, the top one or two threads of the nut are precisely deflected inward at opposing points, creating a slightly non-circular shape. As a standard male bolt thread enters this section, it must elastically deflect the deformed nut threads back into a circular shape. This creates a powerful spring-like clamping force, or friction grip, on the flanks of the bolt threads. This purely mechanical interference creates the "prevailing torque" that resists rotation from vibration. Because this mechanism relies solely on the resiliency of the heat-treated steel, it remains effective at temperatures up to 450°F, far beyond the melting point of a nylon polymer insert.

Note: This is a flight-critical component. It must be tightened using a calibrated torque wrench to the value specified in the applicable maintenance manual. While reusable, the nut must be discarded if its prevailing torque falls below the minimum specified value, which can be checked with a torque wrench before the nut is seated.Alternate Part Numbers: 010210-006, 10121717, 2110063, 2628856, 5310PL0141537, 984050, CIPRD-MS21042-L5, FN12M054, H14-5, MS21042-L5, NAS1291-5, NAS679A5, RM52LH3324-054, T6S524, T98S524

Product Overview

A nut having 6 flat sides and an integral washer that extends beyond the flats or periphery. An integral feature is incorporated for locking on the threads of a mating member.

Item Specification