NAS1149 — Flat Washer Specification
NAS1149 is the National Aerospace Standard covering flat washers for aerospace and defense assembly. Published by the Aerospace Industries Association (AIA), it defines the approved materials, finishes, dimensions, and part-marking codes manufacturers must follow, and is recognized as the direct replacement for the legacy AN960 washer series.
At a Glance
Key identifiers every buyer or engineer needs before specifying NAS1149 hardware.
Overview
What the standard controls and why it matters for defense and aerospace procurement.
NAS1149 is a National Aerospace Standard drawing that sets the acceptable materials, protective finishes, sizing, and identification codes for flat washers used across aerospace structures, engine assemblies, and defense hardware. First approved in March 1990, it has been revised multiple times, with the drawing explicitly stating each revision supersedes all prior versions of the same part six months after approval.
The standard is administered by the Aerospace Industries Association of America (AIA), which also makes clear that use of NAS documents is voluntary and that AIA does not certify supplier conformance — traceability and quality assurance remain the responsibility of the manufacturer and buyer.
A defining feature of NAS1149 is that it was written to be a drop-in successor to the older AN960 washer line: the standard provides matching substitutes for AN960 washers (Revision 20 and later) so designers upgrading legacy drawings can cross into NAS1149 part numbers without a redesign.
- Covers flat washers only — not lock, countersunk, or spherical washers.
- Falls under Federal Supply Classification (FSC) 5310 — Washers.
- Dimensions are specified in inches, with surface texture and geometric tolerancing referenced to ASME B46.1 and ASME Y14.5M respectively.
Part Number Decoder
NAS1149 part numbers encode material, finish, size, and thickness in a single string. Use the selectors below to build and decode an example designation.
Approved Materials & Finishes
Each combination is assigned a specific material and finish code used to build the part number.
| Material | Typical Code | Common Finish Options | Typical Application |
|---|---|---|---|
| Carbon / Alloy Steel | F | Black Oxide, Cadmium Plate | General structural assembly |
| Corrosion Resistant Steel (CRES) | C | Passivate, None | Corrosive / high-vibration environments |
| Aluminum Alloy (2024-T3) | D | Anodize, Chemical Treatment | Weight-critical airframe assembly |
| Brass | BN | None | Electrical / non-magnetic applications |
| Titanium (CP & 6AL-4V) | V | None, Color ID coating | High strength-to-weight, tactical aircraft |
NAS1149 was introduced as the modern successor to AN960 flat washers. The standard's own notes confirm it provides direct substitutes for AN960 washers (Revision 20 and later), so most legacy AN960 callouts can be cross-referenced to an equivalent NAS1149 part — engineers should still confirm size and material interchangeability against the applicable table before substituting on active designs.
Manufacturing & Quality Requirements
Key inspection and workmanship callouts drawn from the standard.
All burrs and sharp edges must be removed, and surface texture is held to 125 microinches per ASME B46.1 unless otherwise specified.
Inside and outside diameters must be concentric within the tolerance of the inside diameter, with geometric tolerancing applied per ASME Y14.5M.
CRES washers are checked for magnetic permeability (below 2.0 relative to air) using a magnetic permeability indicator per ASTM A342.
Lot sampling follows ANSI/ASQ Z1.4 (MIL-STD-105): visual/dimensional inspection at AQL 4.0%, finish inspection at AQL 2.5% — any lot exceeding these limits is rejected.
Titanium washers are tested per Section 4.5 of AMS 2488, and CP or 6AL-4V titanium parts may be color-coded for material identification.
Packaging follows Level A or C, with packing at Level A, B, or C in accordance with ASTM D3951 / PPP-H-1581.
NAS1149 — Frequently Asked Questions
What does NAS1149 cover?
It covers flat washers for aerospace and defense use, defining approved materials, finishes, sizes, thicknesses, and the coding system used to build a compliant part number.
Is NAS1149 the same as AN960?
They are closely related but not identical documents. NAS1149 was developed as the modern replacement for AN960 and provides matching substitutes for AN960 washers from Revision 20 onward, which is why many designs originally called out on AN960 are now specified on NAS1149.
What materials are available under NAS1149?
Carbon and alloy steel, corrosion resistant steel (CRES), 2024-T3 aluminum alloy, brass, and titanium (commercially pure and 6AL-4V), each with its own finish options.
Who publishes and maintains NAS1149?
NAS1149 is published by the Aerospace Industries Association of America (AIA). Use of the standard is voluntary, and AIA does not qualify suppliers or certify conformance of parts made to it — that responsibility sits with the manufacturer and buyer's quality system.
How is a NAS1149 part number structured?
A typical designation reads NAS1149 + material code + size code + thickness code + finish code, e.g. NAS1149F1290B for a carbon steel, black oxide, .750" nominal, .090" thick washer. Try the decoder tool above to see how each segment changes.
Need NAS1149 Washers to Print?
Ananka Fasteners manufactures NAS1149 flat washers with full material traceability and Mill Test Certification for every lot.
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