?unique=3d6d0d4)
AN960KD416L – Aerospace High-Strength Cadmium Plated Flat Washer
Available now on the Airparts.aero Marketplace.
The AN960KD416L is a high-precision, structural flat washer manufactured to the Army-Navy (AN) aeronautical standard. Specifically engineered for the aerospace industry, this washer serves as a critical interface between fasteners and airframe surfaces. The "KD" designation indicates that the washer is fabricated from high-strength carbon steel and finished with a Type II yellow dichromate cadmium plating, providing maximum corrosion resistance and a stabilized friction coefficient during torque application.
As a "Light" (L) series washer, the AN960KD416L features a thinner profile than standard AN960 washers, making it the ideal choice for weight-sensitive applications or areas with limited clearance. Its primary function is to provide a smooth bearing surface, distribute the compressive load of a torqued bolt or nut, and protect the underlying aluminum or composite structure from "marring" or surface deformation. From general aviation piston aircraft to high-performance turbines, the AN960KD416L is a staple in structural joinery, ensuring the longevity and integrity of every bolted connection.
This part has been supersceded by NAS1149D0416K.
Key Features
Supersceded By Part Number: NAS1149D0416K
High-Strength Carbon Steel: Fabricated from heat-treated carbon steel to ensure high compressive yield strength and resistance to "cupping" under load.
Cadmium II Plating: Finished with yellow dichromate cadmium (QQ-P-416 Type II, Class 2) for superior galvanic protection when in contact with dissimilar metals.
Light Profile (L-Series): Reduced thickness compared to standard washers, optimized for weight reduction and tight-clearance installations.
Precision Stamping: Manufactured with controlled tolerances to ensure perfect concentricity and a flat, burr-free bearing surface.
Versatile Application: Compatible with a wide range of AN, NAS, and MS bolts, specifically sized for 1/4" (0.250 inch) nominal diameter fasteners.
Technical Specifications
Part Number: AN960KD416L
Standard: AN960 (Army-Navy)
Material: Carbon Steel
Finish: Cadmium Plate, Type II (Yellow), Class 21
Fastener Size: 1/4 inch (0.250")
Inside Diameter (ID): 0.265 inches (+0.015 / -0.005)2
Outside Diameter (OD): 0.500 inches (+0.000 / -0.015)
Thickness: 0.032 inches (Nominal)
Governing Specifications: MIL-W-12133 (Standard for Flat Washers)
Certification: FAA-PMA / OEM Standard Hardware
Aircraft Compatibility
Cessna 100/200/300/400 Series
Piper PA-28, PA-32, PA-34, PA-44 Series
Beechcraft Bonanza, Baron, and King Air Series
Textron Aviation / Bell Helicopter
Note: AN960 series washers are universal hardware. Always consult the specific aircraft Illustrated Parts Catalog (IPC) to verify the correct washer thickness and material required for your specific station.
Applications
Structural Joinery: Distributing bolt clamping force on fuselage skins and wing ribs.
Engine Baffling: Providing a secure bearing surface for smaller accessory mounts.
Interior Hardware: Securing seat tracks and floor panels where weight is a primary concern.
Why Choose AN960KD416L?
In aerospace maintenance, the integrity of a joint depends on the consistent application of preload. Choosing the genuine AN960KD416L ensures that the washer’s Modulus of Elasticity and surface finish are exactly as specified by the aircraft's original designers. Using "commercial grade" washers can lead to "embedment" or "brinelling," where the washer deforms into the aircraft structure, causing an immediate loss of bolt tension. This loss of preload can lead to fatigue cracking or structural failure. The AN960KD416L provides the documented traceability and metallurgical reliability required to maintain certified aircraft airworthiness.
The AN960KD416L is designed based on the engineering principle of Bearing Stress Distribution. When a bolt is torqued to its specified value, it creates an intense axial load. Without a washer, the small surface area of the bolt head would exert pressure exceeding the Compressive Yield Strength of the underlying aluminum (which is significantly lower than that of steel), leading to surface crushing. By increasing the effective surface area (3$A$), the washer reduces the localized compressive stress (4$\sigma = F/A$).5
The Cadmium plating serves a dual role: it acts as a sacrificial anode to prevent Galvanic Corrosion between the steel washer and the aluminum airframe, and it provides a consistent Nut Factor ($K$). This $K$ factor is essential because it stabilizes the relationship between the torque applied by the mechanic and the actual tension (preload) achieved in the bolt. The "Light" 0.032" thickness is specifically optimized to avoid unnecessary stack-up height in shear joints while maintaining enough Flexural Rigidity to prevent the washer from "dishing" under the clamping force.
Note: The AN960KD416L is a structural fastener component. It must be inspected for any signs of corrosion, pitting, or permanent deformation (cupping) before installation. Reusing washers that have been subjected to over-torque is strictly prohibited. Installation must be performed by a certified A&P mechanic in accordance with FAA Advisory Circular AC 43.13-1B.
