'AN' BOLTS
WARNING: 'AN' (Air Force-Navy) Bolts comply with strict quality standards and are used
throughout the construction of this aircraft for structural integrity. NEVER USE
SUBSTITUTES! See your dealer for replacements if necessary.
If the diameter and length is known and an 'AN' Bolt Gauge is not available remember this easy
method:
The first number following the 'AN' designation is the bolt diameter shank size in 1/16" increments.
AN3 = 3/16”Diameter Shank
AN4 = 4/16" or 1/4" Diameter Shank
AN5 = 5/16" Diameter Shank
If there is a single number following the dash (-), it is the length in 1/8" increments for lengths
LESS than one inch. Example: An 'AN3-7’ Bolt is APPROXIMATELY 7/8" in length.
If there are TWO numbers following the dash (-), the first represents the length in inches and the
second represents the length in 1/8" fractions.
Example: An 'AN4-24' Bolt is APPROXIMATELY 2-4/8" or 2-1/2" in length.
NOTE: To identify the second of TWO digits as an '8' would be incorrect since 8/8” = 1.
A call out of ‘AN5-28’ would be incorrect. The bolt is properly called an 'AN5-30'.
A bolt with a designation of AN3-15A (with an 'A') means NO safety
hole (hole absent) in the BOTTOM of the shank.
A bolt designated as an AN3-15 (without an 'A') means there IS a
safety hole in the BOTTOM of the bolt shank.
WARNING: 'Hardware store' type bolts are of inferior quality and DO NOT meet 'AN' requirements.
They are therefore structurally UNSAFE.
WARNING: NEVER USE a locknut on a bolt that has a hole in the threads as the primary means of
securement unless the hole in the bolt is clearly and completely visible past the
tightened locknut. If the hole in the shank is not clearly visible, the only approved
method of securement (with a hole in the threads) is the use of a castle nut with a
cotter pin (bent correctly).
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