2
Since the member thickness (grip) is given, and the bolt size is given, we can estimate the needed length
of the bolt ensuring that a couple of threads stick out beyond the end of the nut.
From Table (87), page
426, the length of the bolt should exceed the grip, l, plus the nut thickness, H:
L
l
H
+
From Appendix Table (A31) page 1055, for ½ in bolt, the height, H, of a regular hex nut is 7/16 inch.
The grip, called l or L
G
, is the total thickness of material between the nut and the bolt head,
0.5 0.625 1.125 in
G
l
L
=
=
+
=
Therefore, the bolt length, L,
needs to be
1.125 7 /16 1.5625 in
L
+
=
From the standard lengths normally available (See Table (A17), page 1035),
choose L = 1.75 inches
.
This needs to be checked to see how many threads are showing beyond the nut, but it also needs to be
checked to make sure the unthreaded part of the bolt does not extend beyond the grip (that is the threads
on the bolt need to extend far enough so the nut does not bottom out on the threads before the members
are gripped.)
Since the bolt specification is ½ in13, this indicates 13 threads per inch, the thread pitch.
(See Table (82), page 413.)
Therefore the threads showing beyond the nut are:
[ ] [ ]
(
) 13
1.75 1.5625 13
2.44 threads
showing
N
L
l
H
=

+
=

=
This is enough threads showing (2 or more is adequate).
From Table (87), page 426, the threaded
length, L
T
is
2
1/ 4
2(0.5) 1/ 4 1.25 in
T
L
d
=
+
=
+
=
So the length of bolt that is unthreaded is (also from Table (87)):