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NAS1149C0432R – NAS Flat Stainless Steel Washer
Part Number: NAS1149C0432R
Manufacturer: Multiple (Manufactured to National Aerospace Standard)
Standard Series: NAS1149 (Supersedes AN960)
Common Synonyms: Stainless Steel Flat Washer, AN960C416L (Cross-Ref)
Overview Section
The NAS1149C0432R is a high-precision, Corrosion-Resistant Steel (CRES) flat washer manufactured to the National Aerospace Standard. This specific "R" (Regular) thickness washer is engineered to provide a smooth bearing surface under the head of a bolt or nut, distributing the clamping load over a wider area to prevent damage to the airframe skin or structural components.
Unlike commercial-grade washers, the NAS1149 series features strictly controlled inner and outer diameters with precise deburring to ensure they do not introduce stress risers in high-vibration aerospace environments. The "C" designation identifies the material as 300-series stainless steel, making it ideal for use in areas exposed to environmental moisture, exhaust gases, or corrosive fluids.
Enhanced Technical Data
| Technical Metric | Specification Data |
| Material Base | 300 Series Corrosion Resistant Steel (CRES) |
| Passivation | Per AMS2700 (Enhanced Corrosion Protection) |
| Nominal Bolt Size | #4 or 1/4 in (0.250") |
| Inside Diameter (ID) | 0.255 in – 0.275 in |
| Outside Diameter (OD) | 0.495 in – 0.505 in |
| Thickness (Regular) | 0.028 in – 0.036 in (32 Gauge) |
| Hardness | Rockwell B75 to C35 (depending on specific heat treat) |
| Magnetic Permeability | Non-Magnetic (Typical for 300 series CRES) |
| Weight | 0.0014 lbs per unit (approx.) |
Advanced Engineering & Structural Application
The NAS1149C0432R is engineered for Load Distribution and Electrolytic Separation. In aerospace assemblies, the "R" (Regular) thickness is the standard for most structural joints, providing enough rigidity to prevent "cupping" under high torque loads.
Engineering Insight: Material Compatibility
The use of 300 Series Stainless Steel in the NAS1149C0432R is critical when fastening components where galvanic corrosion is a concern. When used with stainless steel bolts (such as NAS1351 or NAS1352) or in carbon-fiber structures, this washer prevents the battery-like effect that causes aluminum parts to corrode.
Dimensional Precision: "Regular" vs. "Light"
The "32" in the part number represents the thickness in thousandths (nominal 0.032"). If your application requires a thinner profile for weight savings or grip-length adjustments, the "L" (Light) version (typically 0.016") would be used. The "R" version is preferred for primary structural joints where maximum clamping surface stability is required.
Aircraft Compatibility
The NAS1149C0432R is an ubiquitous hardware item found in virtually every civil and military aircraft:
Textron Aviation: Standard hardware for Cessna Citation and Beechcraft King Air engine cowlings and fairings.
General Aviation: Extensively used in Piper, Mooney, and Cirrus airframes for landing gear and flight control linkages.
Experimental Aircraft: The standard 1/4" stainless washer for high-quality builds like the Van's RV series.
Marine/High-Moisture Environments: Preferred for seaplanes and aircraft operating in coastal regions.
The NAS1149C0432R is the industry standard for corrosion-resistant hardware in aerospace applications. Whether you are performing a 100-hour inspection or a full structural rebuild, utilizing genuine NAS standard washers ensures your assembly meets the load-distribution requirements specified in the Aircraft Maintenance Manual (AMM). These 300-series stainless steel washers provide the thermal and chemical resistance needed for use in engine compartments and exterior skins. Avoid the risks of hydrogen embrittlement and corrosion common in lower-tier hardware—choose the precision and reliability of the NAS1149C0432R.
Installation & Maintenance Addendum
Burr Orientation: While NAS washers are high-quality, one side often has a slightly smoother radius than the other from the stamping process. Always install the "smooth" side against the aircraft skin to prevent scratching the protective primer or paint.
Torque Verification: Ensure that the thickness of the NAS1149C0432R is accounted for when determining the Grip Length of your bolt. There should be at least two full threads visible beyond the nut.
Reuse Policy: Stainless steel washers can generally be reused if they are flat and free of "scoring" or deformation.5 Discard if the washer shows any signs of "cupping" from over-torquing.
