nonself-locking nuts are used, they should be locked
with an auxiliary locking device such as a check nut or
NUTS.--Nonself-locking nuts require the use of a
lock washer. See figure 3-17.
separate locking device for security of installation.
There are several types of these locking devices
CASTLE NUTS.--These nuts are used with
mentioned in the following paragraphs in connection
drilled shank bolts, hex-head bolts, clevis bolts,
with the nuts on which they are used. Since no single
eyebolts, and drilled-head studs. These nuts are
locking device can be used with all types of
designed to be secured with cotter pins or safety wire.
nonself-locking nuts, you must select one suitable for
CASTELLATED NUTS.--Like the castle nuts,
the type of nut being used.
these nuts are castellated for safetying. They are not as
SELF-LOCKING NUTS.--Self-locking nuts
strong or cut as deep as the castle nuts.
provide tight connections that will not loosen under
CHECK NUTS.--These nuts are used in locking
vibrations. Self-locking nuts approved for use on
devices for nonself-locking plain hex nuts, setscrews,
aircraft meet critical strength, corrosion-resistance, and
and threaded rod ends.
temperature specifications. The two major types of
self-locking nuts are prevailing torque and free
PLATE NUTS.--These nuts are used for blind
spinning. The two general types of prevailing torque
mounting in inaccessible locations and for easier
nuts are the all-metal nuts and the nonmetallic insert
maintenance. They are available in a wide range of
nuts. New self-locking nuts must be used each time
sizes and shapes. One-lug, two-lug, and right-angle
components are installed in critical areas throughout
shapes are available to accommodate the specific
the entire aircraft, including all flight, engine, and fuel
physical requirements of nut locations. Floating nuts
control linkage and attachments. The flexloc nut is an
provide a controlled amount of nut movement to
example of the all-metal type. The elastic stop nut is an
compensate for subassembly misalignment. They can
example of the nonmetallic insert type. All-metal
be either self-locking or nonself-locking. See figure
self-locking nuts are constructed with the threads in the
load-carrying portion of the nut out of phase with the
CHANNEL NUTS.--These nuts are used in
threads in the locking portion, or with a saw cut top
applications requiring anchored nuts equally spaced
portion with a pinched-in thread. The locking action of
around openings such as access and inspection doors
these types depends upon the resiliency of the metal
and removable leading edges. Straight or curved
when the locking section and load-carrying section are
channel nut strips offer a wide range of nut spacing and
forced into alignment when engaged by the bolt or
provide a multinut unit that has all the advantages of
floating nuts. They are usually self-locking.
PLAIN HEX NUTS.--These nuts are available in
BARREL NUTS.--These nuts are installed in
self-locking or nonself-locking styles. When the
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
Figure 3-18.--Self-locking plate nuts.