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Jabiru J450 Constructors Manual
General>Aircraft grade bolts and lock nuts
Tuesday, April 6, 2010
17 of 343
General>Aircraft grade bolts and lock nuts
General
All bolts 3/16” or larger in diameter that have been supplied with your Jabiru kit are Aircraft
grade bolts.
Under
no
circumstances must any bolts other than Aircraft grade bolts be used on your Jabiru.
Aircraft grade bolts are significantly stronger than regular commercial grade bolts and have
features such as corrosion resistance that have been designed specifically for aircraft use.
Aircraft grade bolts are quite different in appearance to regular commercial grade bolts in
several ways: Aircraft grade bolts are usually gold or silver in colour; they have a relatively
short thread length and a longer plain shank or grip length.
In almost all cases the supplied and specified bolts will be the correct length for each task, but
kit builders need to be aware of the correct method of determining and/or checking the correct
length of bolts and also the correct method of tightening lock nuts.
The parts of a bolt
There are 2 variable lengths to an Aircraft
grade bolt: the overall length, usually just
referred to as the
length
, and the
grip length
,
which is the length of the plain shank of the
bolt, which is measured from underneath the
head of the bolt to the beginning of the
threads (see the drawing at right).
The
thread length
is generally fixed in
relation to the diameter of the bolt.
Bolt identification
Aircraft bolts supplied with your Jabiru kit are identified in this Manual and in Jabiru
drawings by the prefix letters “AN”, the diameter (measured in 1/16” increments) and the
length (measured in 1/8” increments) of the bolt and a suffix, which is usually “A”.
Examples of bolt identifiers would be: AN3-6A, AN4-14A, AN3-22A, AN4-72 and so on.
For example, for an
AN3-5A
bolt:
AN
means the bolt has been manufactured to Aircraft (Military) standards
3
the diameter of the bolt in 1/16" increments: (3/16” in this case)
-
5
(the dash number) the length of the bolt in 1/8" increments: (5/8” in this case)
A
not drilled for a lock pin. Bolts with no “A” here are drilled for a lock pin
If the dash number defining the length of the bolt has two digits, the first digit is the length in
whole inches and the second number is the length in additional 1/8" increments. This can
become complex and if you feel the need to delve deeply into the subject you can locate an
AN bolt chart online or purchase an AN bolt gauge from suppliers of Aircraft grade fasteners.
The last example given above (AN4-72) there is no “A” suffix, which indicates that the
threaded end has been drilled during manufacture for a lock pin while the other 3 examples all
have the suffix “A” and do not have provision for a lock pin.