AN3-22A - Aeronautical Standard Undrilled Shank Machine Bolt #10-32

AN3-22A – Aeronautical Standard Undrilled Shank Machine Bolt #10-32

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Overview

The AN3-22A is a flight-critical, mil-spec machine bolt manufactured in accordance with the Aeronautical Standard (AN) specifications. This is not a common hardware store bolt; it is a precision fastener engineered for airframe and powerplant applications where high strength, consistent quality, and absolute reliability are non-negotiable. The "AN3" designation specifies a 3/16-inch (#10) diameter, the "-22" designates the grip length and overall length, and the "A" suffix indicates an undrilled shank and head, signifying its primary design for tension and shear applications where a cotter pin or lock wire through the shank is not required.

Manufactured from high-tensile alloy steel and coated for corrosion resistance, the AN3-22A is a fundamental building block of aircraft assembly. Its dimensions, material properties, thread geometry, and manufacturing processes are rigidly controlled by military specifications to ensure lot-to-lot consistency and predictable performance. This bolt is commonly used in light to medium-load structural applications, securing brackets, mounting accessories, and assembling non-flight-critical and flight-critical components throughout an aircraft.

Key Features

• Mil-Spec Certification: Manufactured in strict accordance with AN (Aeronautical Standard) and MS (Military Standard) specifications.

• High-Strength Alloy Steel: Fabricated from quenched and tempered alloy steel (typically 4130 or 8740) for superior tensile and shear strength.

• Cadmium Plating: Coated with a Type II, Class 3 cadmium plating per QQ-P-416 for exceptional corrosion and galvanic protection.

• Precision Rolled Threads: Features Class 3A Unified National Fine (UNF) threads, which are rolled for superior fatigue resistance compared to cut threads.

• Undrilled Shank ("A"): Indicates a solid, undrilled shank and head, providing maximum bearing surface and shear strength.

• Traceability: Each lot is fully traceable to the manufacturer and material certifications.

Technical Specifications

• Part Number: AN3-22A

• Component Type: Airframe Machine Bolt

• Basic Diameter: 0.1875 - 0.1890 inches (#10)

• Thread Specification: #10-32 UNF-3A

• Material: Alloy Steel, AISI 4130 or 8740 per MIL-DTL-6812

• Finish: Cadmium Plated, Type II (Yellow Chromate), Class 3 per QQ-P-416

• Head Type: AN Hexagonal Head

• Grip Length (shank): 2 1/4 inches (2.250")

• Overall Length: 2 33/64 inches (2.516")

• Minimum Tensile Strength: 125,000 PSI

• Governing Specifications: AN3, MS20003, NASM3

Features and Characteristics

Aircraft Compatibility

• Universal Application: AN bolts are standard hardware used across nearly all certified aircraft, including but not limited to models from Textron Aviation (Cessna, Beechcraft), Piper, Cirrus, Diamond, and experimental aircraft. The specific length (AN3-22A) is called out in various assembly and component drawings.

Note: While this is a standard part, the specific application of the AN3-22A must be verified against the aircraft's Illustrated Parts Catalog (IPC) or maintenance manual. Correct grip length is critical for joint integrity.

Applications

• Structural Assembly: Used in airframe structures for joining aluminum or steel components where a #10 diameter bolt is specified.

• Component Mounting: Securing hydraulic pumps, avionics trays, brackets, inspection panels, and fairings.

• Engine Accessories: Mounting baffles, alternators, vacuum pumps, and other firewall-forward components where this size and strength are appropriate.

• Shear and Tension Joints: Ideal for joints loaded primarily in shear across the shank or in tension along the bolt's axis.

Why Choose AN3-22A?

Using a certified AN3-22A bolt is a fundamental requirement for airworthy repair and assembly. Commercial-grade hardware lacks the material strength, fatigue resistance, and corrosion protection of a true AN bolt. The failure of a single, improperly substituted bolt in a critical location can lead to catastrophic structural failure. The rolled threads, specific alloy steel, heat treatment, and protective plating of an AN bolt are all engineered features that ensure it will perform predictably under the demanding conditions of flight. Sourcing fully certified and traceable AN hardware is a baseline for aviation safety.

The engineering distinction of the AN3-22A lies in its Class 3A thread fit and rolled thread manufacturing process. Unlike commercial bolts (typically Class 2A), the Class 3A specification mandates a tighter tolerance between the bolt's threads and the nut's threads, reducing play and ensuring a more uniform distribution of tensile loads. Critically, the threads are cold-rolled, not cut. This manufacturing process plastically deforms the material to form the thread roots and crests. This cold working induces compressive residual stresses at the thread root, which is the area most susceptible to fatigue crack initiation. These compressive stresses significantly increase the bolt's fatigue life by counteracting the tensile stresses experienced in service, making it far superior to a cut-thread bolt in the high-vibration environment of an aircraft.

Note: This is a flight-critical fastener. Installation must be performed by a certified mechanic in accordance with the aircraft's structural repair or maintenance manual. It is imperative to verify the correct grip length for the specific application; the grip (unthreaded shank) should extend through all layers of the material being joined. Use with a corresponding AN365 nut and AN960 washer. Torque to the values specified in AC 43.13-1B or the manufacturer's manual.

Documentation

• MIL-DTL-6812C: https://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-DTL/MIL-DTL-6812C_55589/

• QQ-P-416F (Plating): http://everyspec.com/QQ-SPECS/QQ-P/QQ-P-416F_22313/

• NASM3 (Standard): A public-facing PDF is not readily available for the latest NASM standards, which are controlled documents. The legacy AN3 specification sheet provides the foundational data.

Features and Characteristics

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