AN3-4A – 10-32 x 1/2" Hex Head Bolt, Alloy Steel, Cadmium Plated
Available now on the Airparts.aero Marketplace.
Overview
The AN3-4A is a high-strength, general-purpose aerospace fastener manufactured to the foundational Air Force-Navy (AN) standard. This hex head bolt is engineered from heat-treated alloy steel for use in a multitude of applications, particularly for clamping thin-gauge materials. With a 3/16-inch diameter and a short 1/2-inch nominal length, this bolt is a staple for assembling a wide range of aircraft components where a longer bolt would be unsuitable. The "A" suffix in the part number signifies an undrilled shank, indicating its design for use with self-locking nuts or other approved locking devices.
Protected by a durable cadmium plating for superior corrosion resistance, the AN3-4A is an essential component for aircraft construction and maintenance. Its adherence to the AN specification ensures complete traceability, uniform quality, and the mechanical performance required for flight-critical installations.
Key Features
High-Tensile Alloy Steel: Fabricated from premium alloy steel (typically 4140 or 8740) and heat-treated to a minimum tensile strength of 125,000 PSI for maximum load-carrying capability.
Cadmium Plating: Coated with a sacrificial cadmium layer per QQ-P-416, providing excellent protection against environmental corrosion and ensuring consistent torque-tension relationships.
Rolled Threads: Features #10-32 UNF-3A threads that are cold-rolled, a superior manufacturing process that increases fatigue resistance exponentially compared to cut threads.
Undrilled Shank ("A" Type): The solid, un-drilled shank is designed for use with a variety of self-locking nuts, providing secure fastening in a wide range of tension and shear applications.
Short Grip Design: A 1/8-inch grip length makes this bolt ideal for securing thin materials, brackets, and clamps without excess threads protruding.
AN Standard Compliance: Guarantees every aspect of the bolt—from material chemistry to dimensional tolerances—meets the rigorous standards required for airworthy components.
Technical Specifications
Part Number: AN3-4A
Component Type: Hex Head Machine Bolt
Governing Specification: AN3 / NASM3
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): 1/2 inch (0.500 inches)
Grip Length (Unthreaded Shank): 1/8 inch (0.125 inches)
Thread Specification: #10-32 UNF-3A
Aircraft Compatibility
The AN3-4A is a universal standard hardware item used across the entire spectrum of aviation, from light piston aircraft to the largest transport category jets. It is specified in countless locations on aircraft manufactured by:
Textron Aviation (Cessna, Beechcraft, Hawker)
Boeing
Airbus
Bombardier
Embraer
Piper, Cirrus, Diamond, and all other major OEMs.
Note: Verification of applicability is the responsibility of the installer. The grip length must be correctly matched to the total thickness of the material being joined. Always consult the current version of the aircraft's Illustrated Parts Catalog (IPC) or maintenance manual to confirm part number eligibility.
Applications
Attaching clamps (P-clamps) for fluid lines and wire bundles.
Securing small brackets, inspection covers, and instrument panels.
Fastening firewall seals, gaskets, and thin metal components.
Assembly of secondary airframe structures and fairings.
Why Choose AN3-4A?
The use of certified aerospace hardware is non-negotiable for flight safety. An AN3-4A bolt guarantees the precise material properties, heat treatment, and manufacturing processes (like rolled threads) that are essential for resisting the unique stresses of flight, including vibration and cyclic loading. The substitution of a commercial-grade bolt, which lacks these controlled attributes, would introduce a direct and catastrophic risk of joint failure. This certified fastener is the only choice for an airworthy repair.
The engineering principle of selecting the correct fastener is exemplified by the specific dimensions of the AN3-4A. The 1/8-inch grip length (the unthreaded portion of the shank) is a critical design feature. In a structurally sound shear joint, the unthreaded shank must extend fully through the materials being fastened. This ensures that shear loads are carried by the full 0.1875-inch diameter of the bolt, maximizing the joint's strength. If a bolt with an insufficient grip length were used, the weaker, notched threads would bear the shear load, creating a stress concentration and significantly reducing the load-carrying capacity and fatigue life of the joint. The AN3-4A is therefore the precisely engineered solution for joining a material stack-up of approximately 1/8-inch thickness.
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 a corresponding certified aerospace-grade self-locking nut (e.g., MS21044N3 or MS21045N3) 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.
Fits In:
- · Bombardier Challenger 601
- · Bombardier Challenger 604
- · Bombardier Challenger 605
- · Bombardier Global Express
- · Bombardier Learjet 40
- · Bombardier Learjet 45
- · Bombardier Learjet 55
- · Bombardier Learjet 60 - all variants
- · Embraer Legacy 600-650
- · Embraer Phenom 300
- · Piaggio Avanti II
- · Piaggio Avanti P180
- · Textron Aviation Beechcraft King Air 100 - all variants
- · Textron Aviation Beechcraft King Air 200 - all variants
- · Textron Aviation Beechcraft King Air 300 - all variants
- · Textron Aviation Beechcraft King Air 90 - all variants
- · Textron Aviation Beechcraft Premier
- · Textron Aviation Cessna 500 Citation I-ISP
- · Textron Aviation Cessna 510 Citation Mustang
- · Textron Aviation Cessna 525 Citation Citationjet
- · Textron Aviation Cessna 550 Citation I-II-Bravo
- · Textron Aviation Cessna 560 Citation V-Ultra-Encore-Excel-XLS
- · Textron Aviation Cessna 650 Citation III-IV-VI-VII
- · Textron Aviation Cessna 680 Citation Sovereign
- · Textron Aviation Cessna 750 Citation X
- · Textron Aviation Hawker 400-400XP
- · Textron Aviation Hawker 800
- · Textron Aviation Hawker 800XP-850XP
- · Textron Aviation Hawker 900XP
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