Learn · Which spec replaces which
AN3 vs NASM3 vs NAS6203 bolts
AN3 thru AN20 was not replaced by NAS6203. It was cancelled on 1 December 1999 and superseded by NASM3 thru NASM20, and the notice says the part numbers are identical: AN6-10 stays AN6-10. NAS6203 thru NAS6220 is a separate standard that the FAA describes as a close tolerance bolt. No public document read for this page says NAS6203 or NAS1103 replaces AN3.[1][2]
Public description
- AN3 thru AN20
- Standard aircraft hex head bolts: all-purpose structural bolts for general applications that require tension or shear loads[2]
- NAS6203 thru NAS6220
- Table 7-12: "Bolt, hex. head, short thread, alloy steel". Para 7-49 calls the NAS6200 series close tolerance bolts. The DoD adoption notice titles the same standard "LONG THREAD". The two public descriptions disagree on thread length; see below.[2][3]
- NAS1103 thru NAS1120
- Bolt, machine, hex head[2]
Document status
- AN3 thru AN20
- Rev 12 cancelled 1 December 1999, superseded by NASM3 thru NASM20. AIA lists NASM3-NASM20 Rev 5, 28 February 2025.[1][4]
- NAS6203 thru NAS6220
- National Aerospace Standard, adopted by the Department of Defense on 14 June 1975.[3]
- NAS1103 thru NAS1120
- Not in a public source: no cancellation notice or DoD adoption record was found
Shank diameter, 1/4 in size
- AN3 thru AN20
- AN4: .249 max, .246 min[5]
- NAS6203 thru NAS6220
- Not in a public source: the NAS6203 sheet was not read
- NAS1103 thru NAS1120
- Not in a public source: the NAS1103 sheet was not read
Strength
- AN3 thru AN20
- AN4 steel: 4,080 lb rated ultimate tensile at the thread root[5]
- NAS6203 thru NAS6220
- Not in a public source: the NAS6203 sheet was not read
- NAS1103 thru NAS1120
- Not in a public source: the NAS1103 sheet was not read
This page reports what public documents print. It does not approve a substitution. The aircraft's IPC, SRM or engineering authority decides what may be installed.
Reference only: the controlling drawing, its process spec and the manufacturer's installation instructions govern. How to use these answers
What the notices and sheets say3
- AN3 thru AN20 Notice 1: "AN3 THRU AN20 REV. 12, dated 14 JANUARY 1991, is hereby canceled and superseded by NASM3 THRU NASM20. The Part Identification Number (PIN) for AN3 THRU AN20 REV. 12 and the part number for NASM3 THRU NASM20 are identical. The part numbers have not been changed."[1]
- FAA AC 43.13-1B, para 7-44: "Do not substitute for close-tolerance fasteners without specific instructions from the aircraft manufacturer or the FAA."[2]
- FAA AC 43.13-1B, para 7-49: "NAS6200 SERIES BOLTS. These are close tolerance bolts and are available in two oversized diameters to fit slightly elongated holes." Its example is NAS6204-6X, a 1/4 inch bolt with a 1/64 inch larger diameter.[2]
More from the documents2
- Two public descriptions of NAS6203 thru NAS6220 disagree on thread length. AC 43.13-1B Table 7-12 says "short thread" for NAS6203-6220 and "long thread" for NAS6604-6620. The DoD adoption notice titles NAS6203 thru NAS6220 "BOLT, HEX HEAD, CLOSE TOLERANCE ALLOY STEEL, LONG THREAD SELF LOCKING AND NON LOCKING". SpecLok has not read the NAS sheet and does not say which description is right.[2][3]
- AIA lists NASM3-NASM20, "BOLT, MACHINE, AIRCRAFT", at Rev 5 dated 28 February 2025.[4]
Not in a public source4
- NAS6203 thru NAS6220 dimensions, tolerances, material, strength and thread length (AIA document, not read).
- Everything about NAS1103 thru NAS1120 beyond the FAA's one-line description.
- Any statement that NAS6203 or NAS1103 may be installed in place of an AN3 series bolt. None was found in a public document.
- The content of NASM3 thru NASM20 Rev 5 (AIA document, not read).
Sources5
Sources
Each number above links to its document. Scanned sheets were read by eye and re-read by OCR; the check script is in the repository under docs/audit-2026-10/reddit-pages.
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