AN Bolt Reference
Aircraft Grade Hardware — Quick Identification Guide
AN Bolt Part Number Decoder
AN3DD14A = 3/16" dia, drilled shank & head, 14/16" grip, no washer under head
Suffix Codes
| AN # | Dia. (in) | Dia. (frac) | Thread (UNF) | Head A/F | Head Ht. | Shank Ø | Min Grip | Max Grip | Wrench Head / Nut | Typical Use |
|---|---|---|---|---|---|---|---|---|---|---|
| AN3 | 0.190 | 3/16" | 10-32 | 0.312" | 0.114" | 0.186–0.190" | -4 | -20 | 5/16" / 3/8" | Light brackets, avionics, nutplates |
| AN4 | 0.250 | 1/4" | 1/4-28 | 0.438" | 0.150" | 0.246–0.250" | -4 | -26 | 7/16" / 7/16" | Control horns, cowling, small fittings |
| AN5 | 0.312 | 5/16" | 5/16-24 | 0.500" | 0.182" | 0.308–0.312" | -4 | -28 | 1/2" / 1/2" | Wing attach, control surface hinges, ribs |
| AN6 | 0.375 | 3/8" | 3/8-24 | 0.562" | 0.214" | 0.371–0.375" | -4 | -28 | 9/16" / 9/16" | Spar attach, engine mount, main landing gear |
AN3 Grip Lengths (10-32)
| Dash # | Grip | Overall Length |
|---|---|---|
| -4 | 1/4" | 11/16" |
| -5 | 5/16" | 3/4" |
| -6 | 3/8" | 13/16" |
| -7 | 7/16" | 7/8" |
| -8 | 1/2" | 15/16" |
| -10 | 5/8" | 1-1/16" |
| -12 | 3/4" | 1-3/16" |
| -14 | 7/8" | 1-5/16" |
| -16 | 1" | 1-7/16" |
| -20 | 1-1/4" | 1-11/16" |
AN4–AN6 Grip Lengths
| Dash # | Grip | Overall Length |
|---|---|---|
| -4 | 1/4" | 11/16" |
| -5 | 5/16" | 3/4" |
| -6 | 3/8" | 13/16" |
| -7 | 7/16" | 7/8" |
| -8 | 1/2" | 15/16" |
| -10 | 5/8" | 1-1/16" |
| -12 | 3/4" | 1-3/16" |
| -14 | 7/8" | 1-5/16" |
| -16 | 1" | 1-7/16" |
| -20 | 1-1/4" | 1-11/16" |
| -24 | 1-1/2" | 1-15/16" |
| -28 | 1-3/4" | 2-3/16" |
Torque Values (in‑lb) — Dry
| AN # | Thread | Min | Max | Typical |
|---|---|---|---|---|
| AN3 | 10-32 | 20 | 25 | 22 |
| AN4 | 1/4-28 | 50 | 70 | 60 |
| AN5 | 5/16-24 | 100 | 140 | 120 |
| AN6 | 3/8-24 | 160 | 190 | 175 |
Self-locking nuts: add 15–20%
Overall length = grip + 0.44"
Wrench Sizes
| AN # | Bolt Head | Nut |
|---|---|---|
| AN3 | 5/16" | 3/8" |
| AN4 | 7/16" | 7/16" |
| AN5 | 1/2" | 1/2" |
| AN6 | 9/16" | 9/16" |
Field ID Hex head, cadmium plated (yellow), UNF fine threads. Raised dash or triangle on head = alloy steel. No mark = low-strength — do NOT use structurally.
Grip Rule Grip must equal stack thickness. Max 1 washer under nut to adjust. Threads must NOT be in shear plane.
Substitution AN → NAS → MS. Never use SAE or hardware-store bolts in structure.
| AN # | Dia. (in) | Dia. (frac) | Thread (UNF) | Head A/F | Head Ht. | Shank Ø | Min Grip | Max Grip | Wrench Head / Nut | Typical Use |
|---|---|---|---|---|---|---|---|---|---|---|
| AN7 | 0.437 | 7/16" | 7/16-20 | 0.625" | 0.246" | 0.433–0.437" | -4 | -28 | 5/8" / 5/8" | Structural fittings, landing gear, engine mount |
| AN8 | 0.500 | 1/2" | 1/2-20 | 0.750" | 0.278" | 0.496–0.500" | -5 | -28 | 3/4" / 3/4" | Heavy structural, engine mounts, main gear attach |
| AN9 | 0.562 | 9/16" | 9/16-18 | 0.875" | 0.311" | 0.558–0.562" | -5 | -28 | 7/8" / 7/8" | Heavy fittings, tail attach, large structural joints |
| AN10 | 0.625 | 5/8" | 5/8-18 | 0.938" | 0.342" | 0.621–0.625" | -5 | -28 | 15/16" / 15/16" | Major structural attach, spar carry-through |
| AN12 | 0.750 | 3/4" | 3/4-16 | 1.125" | 0.406" | 0.746–0.750" | -6 | -28 | 1-1/8" / 1-1/8" | Main spar bolts, heavy structural members |
| AN16 | 1.000 | 1" | 1-14 | 1.500" | 0.530" | 0.996–1.000" | -7 | -28 | 1-1/2" / 1-1/2" | Very heavy structural; rarely used in EAB |
AN7–AN9 Grip Lengths
| Dash # | Grip | Overall Length |
|---|---|---|
| -4 | 1/4" | 11/16" |
| -5 | 5/16" | 3/4" |
| -6 | 3/8" | 13/16" |
| -7 | 7/16" | 7/8" |
| -8 | 1/2" | 15/16" |
| -10 | 5/8" | 1-1/16" |
| -12 | 3/4" | 1-3/16" |
| -14 | 7/8" | 1-5/16" |
| -16 | 1" | 1-7/16" |
| -20 | 1-1/4" | 1-11/16" |
| -24 | 1-1/2" | 1-15/16" |
| -28 | 1-3/4" | 2-3/16" |
AN10–AN16 Grip Lengths
| Dash # | Grip | Overall Length |
|---|---|---|
| -5 | 5/16" | 3/4" |
| -6 | 3/8" | 13/16" |
| -7 | 7/16" | 7/8" |
| -8 | 1/2" | 15/16" |
| -10 | 5/8" | 1-1/16" |
| -12 | 3/4" | 1-3/16" |
| -14 | 7/8" | 1-5/16" |
| -16 | 1" | 1-7/16" |
| -20 | 1-1/4" | 1-11/16" |
| -24 | 1-1/2" | 1-15/16" |
| -28 | 1-3/4" | 2-3/16" |
Torque Values (in‑lb) — Dry
| AN # | Thread | Min | Max | Typical |
|---|---|---|---|---|
| AN7 | 7/16-20 | 450 | 500 | 475 |
| AN8 | 1/2-20 | 480 | 690 | 585 |
| AN9 | 9/16-18 | 800 | 1000 | 900 |
| AN10 | 5/8-18 | 1100 | 1300 | 1200 |
| AN12 | 3/4-16 | 2300 | 2500 | 2400 |
| AN16 | 1-14 | 5000 | 7000 | 6000 |
Self-locking nuts: add 15–20%
Overall length = grip + 0.44"
Wrench Sizes — AN7 Through AN16
| AN7 | AN8 | AN9 | AN10 | AN12 | AN16 | |
|---|---|---|---|---|---|---|
| Bolt Head | 5/8" | 3/4" | 7/8" | 15/16" | 1-1/8" | 1-1/2" |
| Nut | 5/8" | 3/4" | 7/8" | 15/16" | 1-1/8" | 1-1/2" |
Heavy Bolt Notes AN7+ at primary structural joints: spar, gear, engine mount. Confirm hole tolerance: 0.001"–0.003" clearance on shank.
Cotter Pins AN7+ drilled-shank bolts use AN380/AN381 — always install new, never reuse.
AN9 / AN11 AN11 is obsolete; AN9 may be scarce — use MS/NAS equivalent if unavailable. AN → NAS → MS. Never use SAE or hardware-store bolts in structure.