TM 1-1500-204-23-6
CAUTION
New lockwire shall be used for each application. Damage to equipment may otherwise result.
NOTE
All lockwiring and cotter pin installation will be accomplished in accordance with MS33540
Avoid kinks or sharp bends In lockwire.
(1) Use Federal Specification QQ-W-461, carbon steel wire, for normal lockwire applications, use ASTM
A580 or ASTM A313, corrosion-resistant steel wire, where resistance to corrosion Is a desired property.
(2) Use steel corrosion resisting wire, Federal Specification QQ-W-390, for specific applications where
nonmagnetic qualities and heat resisting properties are desired.
NOTE
When safetying vented plugs, caution should be used to ensure that the safety wire is of such a diameter
that It will not completely block the vent hole.
(3) Install lockwire so that when wired bolt, screw, or threaded item begins to loosen, wire will apply a
restraining force In tightening direction. Do not overstress wire. Make certain that the wire Is Installed
and twisted so that the loop around the head stays down, and does not tend to come up over the bolt
head and leave a slack loop.
NOTE
When using castellated nuts, If the slot Is close to the top of the nut, the wire will be more secure If It
passes alongside the stud.
(4) Apply recommended torque values to parts to be secured and align holes before attempting to proceed
with installation of lockwire.
NOTE
The length of pigtail at the twisted end should be 1/4 to 1/2 inch, or 3 to 6 turns This pigtail shall be bent
back or under to prevent It from becoming a snag
c.
Double-Twist Method. The double-twist method is the most common method of securing with lockwire.
Examples of this method are shown in figures 2-78 and 2-79. The following general rules shall apply.
(1) Install lockwire to parts which have a hole diameter of less than 0.045-inch diameter wire
(2) Install lockwire to parts which have a hole diameter of more than 0 045-inch diameter with wire a
minimum diameter of 0.032-inch.
(3) Install lockwire to drilled-head bolts, screws, or other parts which are grouped together, In series rather
than individually.
NOTE
When installing lockwire to widely spaced bolts by the double-twist method, a group of three will be the
maximum number in a series.
When Installing lockwire to closely spaced bolts, the number that can be secured by a 24-inch length
of wire will be the maximum number In a series.
Widely spaced multiple groups shall mean those in which the fastenings are from 4to 6 inches apart.
Lockwiring shall not be used to secure fastenings or fittings which are spaced more than 6 inches apart
unless tie points are provided on adjacent parts to shorten the span of lockwire to less than 6 inches.
CAUTION
Screws in closely spaced geometric patterns which secure hydraulic or air seals hold hydraulic pressure, or
are used in critical areas of clutch mechanisms and super-chargers should use the double-twist method of
lockwiring to prevent lockwire failure
2-77
