TM 1-1500-204-23-6
i.
External Wrenching Bolts. External wrenching
bolts (12 point), as shown in figure 2-6, are high-strength
bolts used primarily in tension applications. They are
furnished with either drilled or undrilled heads. The
radius under the head of this bolt requires a high tensile
countersunk
washer
(MS20002)
to
be
used
in
conjunction with this bolt. Do not substitute a common
aircraft bolt for a high tensile bolt.
j.
Self-Retaining Bolts. Self-retaining bolts can be
used on rotating controls as specified in the applicable
aircraft maintenance manual. They are primarily
intended for use in shear application at dynamic joint
assemblies of aicraft where the failure of cotter pin or
safety wire would effect safety of flight or endanger
personnel. Self-retaining bolts are installed with
boltheads facing the direction of rotation.
The two types of self-retaining bolts used are positive
retention and impedance.
(1) Positive retention bolts (Figure 2-8A) have a
pawl at threaded end of bolt shank. The pawl is spring
loaded to an extended position. When extended, the
pawl prevents the nut from being removed. Finger
pressure compresses the pawl for removal of the nut
and bolt from the part.
(2) Impedance bolts (Figure 2-8A) have either
spring-loaded balls or a spring ring on the bolt shank
above the threads. These retaining elements extend the
diameter of the bolt and prevents it from sliding from the
component.
k.
Clevis Bolts. Clevis bolts, as shown in figure 2-
7, are used in applications subject to shearing stress
only. They are frequently used as mechanical pins in
control systems. The head is round and slotted.
I.
Eye Bolts. Eye bolts, as shown in figure 2-8,
are used to carry external tension loads and for
attachment of such devices as the clevis, cable shackle,
or fork of a turnbuckle.
CAUTION
Self-locking bolts will not be reused in
flight essential applications, such as
flight and engine controls and single
bolted structural joints which serve as a
primary
load
path.
Damage
to
components may otherwise result
m. Self-Locking Bolts. Self-locking bolts are used
on aircraft to provide tight assemblies which will resist
severe vibration conditions. The locking element is a
nylon (or equivalent) pellet, as shown in figure 2-9,
inserted in the threaded section of the bolt. The locking
action of the pellet takes place at point of engagement
of the screw or nut section. Except as stated in caution
above, self-locking bolts are reusable since the nylon-
locking element is not cut by the threads upon
engagement but merely pressed into the threads. The
threads of the bolts used shall show no distinction or
scratches deep enough to reduce the efficiency of the
threads. The threads of the bolts shall remain in a
serviceable condition and shall permit freely there
installation with fingers of a new nut up to the self-
locking device.
Figure 2-6. External Wrenching Bolt
Figure 2-7. Clevis Bolt
Figure 2-8. Eye Bolt
Change 1 2-18
