and temperature specifications. The two major types
of self-locking nuts are prevailing torque and free
spinning. The two general types of prevailing torque
nuts are the all-metal nuts and the nonmetallic insert
nuts. New self-locking nuts must be used each time
components are installed in critical areas throughout
the entire aircraft, including all flight, engine, and fuel
control linkage and attachments. The flexloc nut is an
example of the all-metal type. The elastic stop nut is
an example of the nonmetallic insert type. All-metal
self-locking nuts are constructed with the threads in
the load-carrying portion of the nut out of phase with
the threads in the locking portion, or with a saw cut
top portion with a pinched-in thread. The locking
action of these types depends upon the resiliency of
the metal when the locking section and load-carrying
section are forced into alignment when engaged by
the bolt or screw threads.
PLAIN HEX NUTS.These nuts are available
in self-locking or nonself-lotting styles. When the
nonself-locking nuts are used, they should be locked
with an auxiliary locking device such as a check nut
or lock washer. See figure 2-26.
CASTLE NUTS.These nuts are used with
drilled shank bolts, hex-head bolts, clevis bolts,
eyebolts, and drilled-head studs. These nuts are
designed to be secured with cotter pins or safety wire.
CASTELLATED SHEAR NUTS.Like the
castle nuts, these nuts are castellated for safetying.
They are not as strong or cut as deep as the castle nuts.
CHECK NUTS.These nuts are used in locking
devices for nonself-locking plain hex nuts, setscrews,
and threaded rod ends.
PLATE NUTS.These nuts are used for blind
mounting in inaccessible locations and for easier
maintenance. They are available in a wide range of
sizes and shapes. One-lug, two-lug, and right-angle
shapes are available to accommodate the specific
physical requirements of nut locations. Floating nuts
provide a controlled amount of nut movement to
compensate for subassembly misalignment. They can
be either self-locking or nonself-locking. See
CHANNEL NUTS.These nuts are used in
applications requiring anchored nuts equally spaced
around openings such as access and inspection doors
and removable leading edges. Straight or curved
channel nut strips offer a wide range of nut spacings
and provide a multinut unit that has all the advantages
of floating nuts. They are usually self-locking.
BARREL NUTS.These nuts are installed in
drilled holes. The round portion of the nut fits in the
drilled hole and provides a self-wrenching effect.
They are usually self-locking.
nuts are generally used where a nut with a high tensile
strength is required or where space is limited and the
use of external-wrenching nuts would not permit the
use of conventional wrenches for installation and
removal. This is usually where the bearing surface is
counterbored. These nuts have a nonmetallic insert
that provides the locking action.
Figure 2-27.Self-locking nuts.