NAS1149F0663P - Flat Washer

NAS1149F0663P – 3/8" CRES Flat Washer (.063" Thick)

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Overview

The NAS1149F0663P is a high-quality, precision flat washer manufactured to the National Aerospace Standard (NAS1149), which has superseded the legacy AN960 specification. This component is fabricated from Corrosion Resistant Steel (CRES), also known as stainless steel, making it the superior choice for installations requiring enhanced corrosion protection or for use with CRES fasteners. Its primary engineering functions within a bolted joint are to distribute the fastener's clamp load over a larger area, provide a smooth and hard bearing surface for consistent torque application, and to protect the underlying structure from damage.

As a component governed by a national aerospace standard, the NAS1149F0663P guarantees precise dimensional tolerances, verified material composition, and the full traceability required for installation on certified aircraft. It is a fundamental hardware item essential for the structural integrity and longevity of countless airframe and powerplant assemblies.

Key Features

• Corrosion Resistant Steel (CRES): Manufactured from a 300-series stainless steel alloy, providing excellent, inherent resistance to oxidation and environmental corrosion.

• Passivated Finish: The surface is passivated in accordance with aerospace standards, creating a passive oxide layer that further enhances corrosion resistance and removes surface contaminants.

• Load Distribution: Prevents the high pressure of a torqued bolt head or nut from galling, crushing, or damaging softer structural materials like aluminum alloys.

• Optimized Bearing Surface: Provides a smooth, hard, and uniform surface for the turning fastener, which is critical for converting applied torque into the correct bolt preload (clamp force).

• Standard Thickness: This is a "-63" washer, indicating a nominal thickness of 0.063 inches, which is the standard-duty thickness for a 3/8-inch bolt application.

• NAS Standard Compliance: Ensures the highest standards of quality control for dimensions, material, and finish, making it a fully airworthy component.

Technical Specifications

• Part Number: NAS1149F0663P

• Component Type: Flat Washer

• Governing Specification: NAS1149 (supersedes AN960C)

• Material: Corrosion Resistant Steel (CRES), 300-Series

• Finish: Passivated per AMS-QQ-P-35

• Intended Bolt/Screw Size: 3/8 inch

• Inside Diameter (ID): 0.406 inches

• Outside Diameter (OD): 0.812 inches

• Nominal Thickness: 0.063 inches

Aircraft Compatibility

The NAS1149F0663P is a universal, standard-issue hardware component used across the entire aerospace industry on virtually all types of aircraft, including:

• Commercial and Transport Category Aircraft (Boeing, Airbus)

• Military Fighter, Bomber, and Transport Aircraft

• Business and Corporate Jets (Textron Aviation, Bombardier, Gulfstream)

• General Aviation (Piston and Turbine) and Rotorcraft

Note: Verification of applicability is the responsibility of the installer. Always consult the current version of the aircraft's Illustrated Parts Catalog (IPC) and maintenance manual to confirm part number eligibility.

Applications

• For use under the heads of bolts and nuts in airframe, powerplant, and systems installations.

• Particularly specified where CRES fasteners are used, to prevent galvanic corrosion between dissimilar metals.

• Essential for creating a reliable fastener stack-up when joining materials of differing hardness.

• Can be used as a precision shim in certain approved applications.

Why Choose NAS1149F0663P?

A bolted joint's ability to maintain its clamp load is critical to flight safety. The use of a certified NAS1149 washer is essential for this function. A non-certified, commercial-grade washer can introduce significant risk due to incorrect material (causing galvanic corrosion), improper hardness (leading to yielding and preload loss), or inaccurate dimensions. This certified NAS washer guarantees that the material is correct, the dimensions are precise, and the finish is controlled, ensuring the joint can be assembled to the exact specifications of the aircraft's design engineers.

The NAS1149F0663P washer is a critical component for controlling the torque-tension relationship in a bolted joint. The fundamental goal of torquing a fastener is to achieve a specific bolt elongation, or preload. A significant portion of the applied torque (often over 80%) is dissipated by friction, primarily under the turning nut or bolt head. The hard, smooth, passivated surface of this CRES washer provides a consistent and predictable coefficient of friction. This tribological consistency is vital, as it ensures that the torque values specified in the maintenance manual are reliably and repeatably converted into the intended axial bolt tension (clamp force). Without a certified washer, friction becomes a highly variable and uncontrolled factor, which can lead to a dangerously under-loaded joint (insufficient clamp) or an over-loaded joint (yielded bolt), even when using a calibrated torque wrench.

Note: This is a flight-critical hardware component and an integral part of a fastener assembly. Washers should be clean and free of defects before installation. If the maintenance manual or engineering drawing specifies a washer for a joint, it must not be omitted. Always use the correct size and material as called for in the approved documentation.

Documentation

The base standard for this part is the National Aerospace Standard NAS1149. This is a controlled document managed by the Aerospace Industries Association (AIA) and is the successor to the AN960 standard.