Everything you need to select the right bolt, nut, or washer — spec system differences, cross-reference equivalents, material properties, and project-specific hardware lists. No competitors have this page. That's the point.
These three specification systems aren't interchangeable labeling — they represent different governing bodies, dimensional standards, and performance tiers. Getting this wrong means rework, or worse, an airworthiness issue.
The original aviation fastener standard developed jointly by the Army and Navy in the 1940s. AN specs define the most common bolts, nuts, washers, and rivets used in general aviation and military aircraft. If you're building or maintaining a certificated GA aircraft, AN is usually your default.
Military Standard specs replaced many AN numbers and extended coverage into higher-performance applications. MS parts often supersede AN equivalents — the MS20073 bolt is the direct replacement for AN3, not a different part. Military and commercial transport programs specify MS because of tighter tolerances and broader environmental coverage.
Issued by the Aerospace Industries Association, NAS specs cover higher-performance fasteners with tighter tolerances than AN or MS — particularly Hi-Lok pins, close-tolerance bolts, and specialty washers. NAS parts dominate structural applications in commercial transports and modern business jets where weight-to-strength ratio matters.
Common equivalencies between spec systems for bolts, nuts, and washers. Search by any part number — AN, MS, or NAS. Not all parts have equivalents across all three systems.
| AN | MS Equivalent | NAS Equivalent | Type | Notes | Shop |
|---|---|---|---|---|---|
| AN3 | MS20073 | NAS6703 | Hex Bolt | 3/32" shank · MS20073 is direct supersedure of AN3 | Shop AN3 → |
| AN4 | MS20074 | NAS6704 | Hex Bolt | 1/4" shank · most common GA bolt size | Shop AN4 → |
| AN5 | MS20073-5 | NAS6705 | Hex Bolt | 5/16" shank · spar attach, engine mount common | Shop AN5 → |
| AN6 | MS20073-6 | NAS6706 | Hex Bolt | 3/8" shank · main landing gear, engine mounts | Shop AN6 → |
| AN7 | MS20073-7 | NAS6707 | Hex Bolt | 7/16" shank · heavy structural / prop flange | Shop AN7 → |
| AN8 | MS20073-8 | NAS6708 | Hex Bolt | 1/2" shank · prop hubs, engine crankcase | Shop AN8 → |
| AN43 | — | NAS43 | Close-Tolerance Bolt | No MS equiv · tighter shank tolerances for shear joints | Shop NAS43 → |
| AN365 | MS21042 | NAS1021 | Self-Locking Nut | AN365 = fiber insert / MS21042 = all-metal · not interchangeable for high-temp | Shop Locknuts → |
| AN310 | MS17826 | — | Castle Nut | Used with cotter pin (AN380) · control rod ends, turnbuckles | Shop AN310 → |
| AN316 | MS21083 | — | Check Nut (Jam) | Locknut for cable fittings, rod-end bearings, turnbuckle barrels | Shop AN316 → |
| — | MS21042 | NAS1021 | All-Metal Locknut | High-temp to 450°F · engine compartment, exhaust areas · replaces AN365 at temp | Shop MS21042 → |
| AN960 | MS15795 | — | Flat Washer (Standard) | Standard diameter · bolt bearing surface, stack-up shimming | Shop AN960 → |
| AN970 | MS15795-X | — | Flat Washer (Wide) | Large OD for wood/composite bearing · EAB wing ribs, wood spars | Shop AN970 → |
| — | — | NAS1149 | CRES Flat Washer | Corrosion-resistant steel · no AN/MS equiv at same spec · wet wing areas, bilge | Shop NAS1149 → |
| AN470 | MS20470 | — | Solid Rivet (Universal) | Universal head · skin, rib flanges where both sides accessible | Shop AN470 → |
| AN426 | MS20426 | — | Solid Rivet (Countersunk) | 100° flush head · outer skin for aerodynamic surfaces, leading edges | Shop AN426 → |
⟳ "—" means no direct equivalent exists in that spec system for the same function. Verify any substitution against the applicable maintenance manual supersedure list. This table covers the most common AN/MS/NAS equivalencies — full mapping requires the current DOD QML and NAS publication index.
All parts in this guide are stocked as certified surplus — 30–50% below Aircraft Spruce pricing.
The material designation is baked into the AN/MS part number suffix. Getting this wrong doesn't fail a visual inspection — it fails under load, in a corrosive environment, or after 200 heat cycles. Know what you're installing.
Selecting the wrong locknut isn't a torque issue — it's a failure mode. AN365 fiber locknuts lose locking action above 250°F. MS21042 all-metal nuts require more torque but survive engine compartment temperatures. Castle nuts need cotter pins and don't belong in vibration-only applications.
"What do I need for X?" — Four common aircraft projects with their primary fastener requirements. These aren't exhaustive bills-of-materials; they're starting points. Always cross-check your specific IPC or AC 43.13-1B for dimensional callouts.
The highest-loaded joint on a GA aircraft. Spar attach bolts see both tension and shear under positive-g loads. No margin for wrong spec, wrong material, or wrong torque. AC 43.13-1B Chapter 7 governs.
Every fastener in or adjacent to a fuel tank must be corrosion-resistant. Cadmium-plated alloy steel corrodes rapidly in aviation fuel environments; CRES or passivated stainless is the correct spec. Fuel cap retention, sender flanges, sump drains.
Flight control hardware sees continuous cyclic loads — every hinge, rod-end, and bellcrank attach point is a fatigue point. Cotter pins and castle nuts are the standard lockout; AN365 works at hinge attach where temperature isn't a concern.
Everything firewall-forward lives in a high-heat, high-vibration environment with motor oil and exhaust gases. Fiber insert locknuts will soften and lose grip — all-metal MS21042 is required in this environment. Safety wire is the preferred lockout for accessory bolts.
Every part in this guide is stocked as certified surplus — FAA 8130-3 traceable, ships from South Florida.