AN3-5A – 10-32 x 5/8" Hex Head Bolt, Alloy Steel, Cadmium Plated
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Overview
The AN3-5A 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 countless structural and systems applications requiring robust clamping force and reliability. With a 3/16-inch diameter and a 5/8-inch nominal length, this bolt is a staple for assembling a wide range of aircraft components. 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 AN3-5A is one of the most common fasteners in aviation. 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.
General Purpose Design: A ubiquitous fastener used in thousands of applications throughout all types of aircraft.
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: AN3-5A
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): 5/8 inch (0.625 inches)
Grip Length (Unthreaded Shank): 1/4 inch (0.250 inches)
Thread Specification: #10-32 UNF-3A
Aircraft Compatibility
The AN3-5A 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
Mounting of avionics trays, brackets, and instruments.
Assembly of secondary airframe structures and fairings.
Engine baffling, cowling, and firewall attachments.
Securing of interior components, systems hardware, and inspection panels.
Why Choose AN3-5A?
The use of certified aerospace hardware is non-negotiable for flight safety. An AN3-5A 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 exceptional fatigue resistance of the AN3-5A bolt is a direct result of the cold rolling process used to form its #10-32 UNF-3A threads. Unlike a subtractive machining process that cuts through the material's grain structure and creates stress risers, cold rolling is a forming process. The bolt blank is pressed between hardened dies, which plastically deforms the steel and forces the grain structure to flow continuously along the contour of the thread. This action induces a high magnitude of compressive residual stress at the thread root, which is the most common point of fatigue crack initiation in a fastener. This compressive stress acts to counteract the tensile stresses from cyclic service loads, significantly increasing the bolt's resistance to fatigue failure and extending its operational life in the demanding, high-vibration environment of an aircraft.
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
Technical Features
- Military Standard Aircraft Machine Bolt
- Hexagon Head
- Undrilled Head
- No Cotter Pin Hole
- Fine Threads
- UNF-3A
- Material: Steel
- Major Diameter: 0.19 in.
- Thread Per Inch (TPI): 32
- Length: 0.656 in.
- Grip Length: 0.25 in.
- Industry Standard Specification: AIA/NAS NASM3-20