Figure 2-72. Turnbuckle Terminals (Sheet 2 of 2)
Lockring Fastener. The lockring, as shown in figure 2-74, is an accessory part used as an anti-rotation
device for screw thread inserts, studs, and many other externally threaded fastening devices. It is serrated both
internally and externally. The internal serrations are configured to mesh with those on the insert flange. The external
serrations are relieved on the entering side so as to form a pilot to permit initial engagement internally. In addition, there
is a 10-degree rake angle on the external serration so that the effect of a broach is duplicated when the ring is pressed or
driven into the counterbored region in the receiving material. The crest of the serrations cuts a series of longitudinal
grooves, thus creating a composite shear area for resistance to rotation, as shown in figure 2-75.
Fittings. The following paragraphs identify tubing and hose fittings used in Army aircraft hydraulic,
pneumatic, and oxygen systems. Figure 2-76 shows typical aircraft fittings.
Fitting Identification. The dash number after the basic number indicates the size, In sixteenths of an inch, of the
tubing or hose for which the fitting is made. The measurement is for the outer diameter of tubing and the inner diameter
of hose. Pipe threads are identified by a dash number which indicates the pipe size in eights of an inch. The material
code is given in table 2-17. For example, AN776-6D indicates an aluminum alloy elbow for tubing 6/16 (3/8) inch in
diameter. Table 2-18 lists aircraft fittings.
Table 2-17. Fittings Material Code
Practices for Installation of Cotter Pins and Lockwire. Installation of cotter pins and safetying methods
are covered by the following paragraphs.
Cotter Pin Installation. Cotter pins shall be installed as follows