STANDARD TORQUE TABLE
Nuts are properly installed when
Refer to tables D-l through D-6 for
all threads are engaged and the bolt chamfer
standard torque limits for threaded fasteners,
extends thru the nut. When flat-end bolts are
hose and tube coupling nuts, bulkhead fit-
tings, and pipe thread fittings, and the
used, the threaded end must extend at least
minimum breakaway torque values for deter-
1/32 inch thru the nut.
mining reusability of self-locking nuts. These
(6) Threads shall be clean and dry
standard torque values apply only when
before installation. If threads are lubricated,
special torque values are not specified in pro-
torque limits are reduced by 30 percent.
cedures. General instructions for installation
and fit of threaded fasteners are as follows:
The tightening sequence in multi-
ple fitting installation is as follows:
Thread shall not be in bearing
when thickness of sheet or fitting is 3/32-inch
Finger tighten all bolts or nuts.
or less. If thickness is more than 3/32-inch, a
maximum of two threads in bearing is per-
Snug up opposite bolts or nuts
In shear applications, thread shall
not be in bearing regardless of material
Tighten opposite bolts or nuts
all around to proper torque. Do not torque ad-
jacent bolts or nuts in sequence.
Washers are used for the following
(8) All-metal self-locking nuts shall
be replaced with new identical parts at each
To compensate for differences in
installation. If new nuts are not available, all
bolt grip length and material thickness due to
metal self-locking nuts may be reused. The
manufacturing tolerances, protective coating,
reused nuts must meet the required minimum
and other surface variances.
friction torque. See Fiction Torque in Inch-
To distribute bearing load over
a greater area to prevent damage to material
Additional standards to be followed
under a bolt head or nut.
are outlined below.
To protect the material surface
Torque limits apply to nut tighten-
when a bolt or nut is tightened.
ing only. When tightening bolt, the higher
limit 10 percent is used.
Prevent galling of aluminum or
other soft material when bolt or nut is tighten-
(2) Torque values are for dry
(unlubricated) threads. If threads are
lubricated, limit is 70 percent unlubricated
(e) To insulate dissimilar metals to
prevent corrosion. The washer material
should be similar to the material on which it
Maximum torque allowed for cot-
rests rather than the bolt or nut material. This
ter pin hole alignment. If limit is exceeded,
insures that if corrosion occurs, it will be bet-
discard nut and bolt and inspect parts secured
ween the bolt and washer, which can be
by the nut and bolt.
Torque limits apply only to
When nut-bolt assemblies are in-
tightening nut on stud.
stalled, the nut shall not engage the first in-
complete thread next to the bolt shank.