AN3-21 - Textron Aviation OEM Undrilled Shank Machine Bolt

AN3-21A – Textron Aviation OEM 10-32 x 2-1/8" Hex Head Bolt

Available now on the Airparts.aero Marketplace.

Overview

The AN3-21A is a fundamental, high-strength aerospace fastener, supplied with the full backing and traceability of Textron Aviation OEM certification. This bolt is manufactured to the rigorous Air Force-Navy (AN) standard, which defines every aspect of its design, from the specific chemistry of its alloy steel to the manufacturing process of its threads. With a 3/16-inch diameter and a 2-1/8-inch nominal length, this fastener is used in countless structural and non-structural applications across the Textron Aviation fleet and beyond.

As an "A" designated bolt, it features an undrilled shank, indicating its design for use with self-locking nuts or other locking devices. Its construction from 125,000 PSI tensile strength alloy steel makes it suitable for both tension and shear loads. Sourcing this part as a Textron Aviation OEM component ensures it is the exact, factory-specified hardware for maintaining the type-certified design and integrity of Cessna, Beechcraft, and Hawker aircraft.

Key Features

• High-Tensile Alloy Steel: Forged from premium alloy steel (typically 4140 or 8740) and heat-treated to a minimum tensile strength of 125,000 PSI.

• Cadmium Plated for Corrosion Resistance: Coated with a sacrificial cadmium layer per QQ-P-416 for exceptional protection against environmental corrosion and to provide consistent lubricity for accurate torqueing.

• Rolled Threads for Superior Fatigue Life: Features #10-32 UNF-3A threads that are cold-rolled, not machine-cut. This process creates a stronger thread root that is highly resistant to fatigue failure from vibration.

• Undrilled Shank ("A" Type): Designed for use with self-locking nuts (e.g., AN365, MS21044), providing secure fastening in a wide range of applications.

• Textron Aviation OEM Certified: Guarantees the component is a factory-approved, fully traceable part for the entire Textron Aviation family of aircraft.

• AN Standard for Full Traceability: Meets all dimensional, material, and quality requirements of the AN3 specification, ensuring airworthiness and interchangeability.

Technical Specifications

• Part Number: AN3-21A (conforms to the AN3-21 callout with an undrilled shank)

• Component Type: Hex Head Machine Bolt

• Governing Specification: AN3 / NASM3

• OEM Authority: Textron Aviation

• Material: Alloy Steel (e.g., 4140, 8740), heat-treated

• Minimum Tensile Strength: 125,000 PSI

• Finish: Cadmium Plate per QQ-P-416, Type II, Class 2

• Diameter: 3/16 inch (0.1875 inches)

• Nominal Length (under head to end): 2-1/8 inches (2.125 inches)

• Grip Length (Unthreaded Shank): Approximately 1.766 inches

• Thread Specification: #10-32 UNF-3A

Aircraft Compatibility

As a Textron Aviation OEM part, this fastener is specified in numerous locations across their entire product line. As an AN-standard bolt, its use is ubiquitous throughout the aerospace industry.

• Primary Textron Aviation Platforms:

  • Cessna Piston Aircraft (172, 182, 206, etc.)

  • Beechcraft Piston Aircraft (Bonanza, Baron)

  • Cessna and Beechcraft Turboprops (Caravan, King Air)

  • Cessna Citation Business Jets

  • Hawker Business Jets

• General Aviation Usage: Used in virtually every class of aircraft for myriad applications.

Note: Verification of applicability is the responsibility of the installer. The grip length must be appropriate for the material thickness being joined. Always consult the current version of the aircraft's Illustrated Parts Catalog (IPC) or maintenance manual to confirm part number eligibility.

Applications

• Assembly of primary and secondary airframe structures

• Engine baffling, cowling, and firewall attachments

• Mounting of flight control components and brackets

• Installation of fairings and inspection panels

• Securing of landing gear components and doors

Why Choose this AN3-21A?

This component carries the dual assurance of meeting the public AN aerospace standard and the specific endorsement of Textron Aviation. This guarantees the bolt's mechanical properties, from the chemistry of its steel to the fatigue-resistance of its rolled threads. Using commercial-grade hardware in an aircraft application introduces an unacceptable risk of material fracture and joint failure. By choosing this OEM-certified AN bolt, you ensure the use of a traceable, airworthy component that maintains the aircraft's original design integrity.

The engineering superiority of an AN3-21A bolt over a commercial equivalent is rooted in its material properties and manufacturing methods. The use of a high-purity alloy steel like 4140 or 8740 allows for a deep and uniform hardness to be achieved during the quench and temper process, ensuring the 125,000 PSI tensile strength is consistent through the bolt's entire cross-section. Critically, in shear joint applications, the grip length (the unthreaded shank) is designed to carry the load. It is imperative that the grip of the bolt extends fully through all layers of the material being fastened. Allowing the weaker, notched threads to bear a shear load can reduce the joint's ultimate strength by up to 30% and create a stress concentration that leads to premature fatigue failure. The precise grip length of a specified AN bolt ensures this unsafe condition is avoided.

Note: This is a flight-critical hardware component. Installation must be performed by a certified mechanic. A calibrated torque wrench must be used to apply the correct torque value specified in the maintenance manual to achieve proper clamp load (preload). This bolt must be paired with an appropriate aerospace-grade self-locking nut (e.g., AN365, MS21044) to ensure the joint remains secure.

Documentation

The specifications for this fastener are maintained under the National Aerospace Standards (NASM), which have superseded many of the original AN drawings. Publicly accessible summaries of these standards can often be found through standards organizations and authorized hardware suppliers.