The
Use of Lock Wire - A Guide
Lock wiring* is the securing
together of two or more parts with a wire which shall be installed in such
a manner that any tendency for a part to loosen will be counteracted by
an additional tightening of the wire.
For general purpose lock
wiring, use the preferred sizes in Table 1-1. Use smaller diameter wire
where parts are too small to permit a hole diameter to accommodate the
preferred sizes, or where space limitations preclude the use of the preferred
sizes. The larger sizes are used where stronger wire is required. Wire
diameter of .032 is the most commonly used.
The common method of installing
lock wire shall consist of two strands of wire twisted together (so called
"Double Twist" method). (One twist is defined as being produced by twisting
the wires through an arc of 180 degrees and is equivalent to half of a
complete turn.) The single strand method of lock wiring may be used for
some applications, such as in a closely spaced, closed geometrical pattern
(triangle, square, rectangle, circle, etc.) parts in electrical system.
Where multiple groups are
locked by either the double twist or the single strand method, the maximum
number in a series shall be determined by the number of units that can
be lock wired by a twenty-four inch length of wire.
Wire shall be pulled taut
while being twisted. The number of twists per inch as recorded in Table
1-1, represents general practice and is given as guidance information only.
Caution must be exercised
during the twisting operation to keep the wire tight without overstressing.
Abrasions caused by commercially available wire twisting pliers shall be
acceptable but nicks, kinks, and other damage to the wire are not.
Lock wire shall not be installed
in such a manner as to cause the wire to be subjected to chafing, fatigue
through vibration, or additional tension other than the tension imposed
on the wire to prevent loosening. In the event that no wire hole is provided,
wiring should be to a convenient neighboring part in a manner so as not
to interfere with the function of the parts. Hose and electrical coupling
nuts shall be wired in the same manner as tube coupling nuts.
Various examples of lock
wiring are shown in Figures 1-1 through 1-12. Figure 1-12 shows the single-stranded
method, while the other figures show the two-stranded or double twist method.
Detailed Instructions
For The Installation Of Lock Wire
Check the units to be lock
wired to make sure that they have been correctly torqued. Under-torquing
or over-torquing to obtain proper alignment of the holes is not advisable.
If it is impossible to obtain a proper alignment within the specified torque
limits, back off the unit and try it again or select another unit.
In adjacent units, it is
desirable that the holes be in approximately the same relationship to each
other as shown in Figures 1-1 through 1-4 (for right-hand threads), thus
the lock wire will have a tendency to pull the unit clockwise. This should
be reversed for left-handed threads.
Where lock wire is used to
secure a castellated nut on a threaded item, selection of locking hole
diameter for the item shall be based on cotter pin requirements.
Table 1-1
Lockwire and Lockwire
Hold Data
