TM 55-2840-231-23
(1) Before tightening, be sure that all threads and that all sealing and mating surfaces are clean
and free of nicks, burrs, and scratches.
(2) Lubricant used on threads will be the same as that used in the engine oil system. Do not
lubricate electrical connectors.
(3) Open-end wrenches with 15° offset angled heads will normally be used for wrench-me
tightening.
b.
When specified in the assembly or installation procedures, use the following procedures to tighten
threaded parts.
NOTE
The snug (no torque) condition is reached when a
positive increase in resistance (on the nut) to turn-
ing is felt (greater than run-on torque), when parts
appear to be properly seated, and when no looseness
between mating parts is noted.
(1) Tightening to 15° wrench arc.
(a) Snug the nut.
(b) Place an open-end wrench on nut.
(c) Establish a line of sight using wrench handle.
(d) Use the angular difference between handle and wrench flats (15°) to visually measure
amount that the nut will have to be turned.
(e) Turn wrench until flats on nut (engaged by wrench) are alined with line of sight estab-
lished by handle in step (c).
(2) Alternate method for tightening to 15° wrench arc.
(a)
(b)
(c)
(d)
Snug the nut.
Place an open-end wrench on nut.
Use the engaged nut flats to establish a line of sight.
Turn wrench until handle is alined with line of sight,
(3) Tightening to 60° and 120°wrench arc. In this method of tightening, primarily used for tube
fittings, the flats on the union are-used as a reference. Wrenches other than open-end wrenches (crowfeet
or tubing wrenches) may be used.
(a) Snug the nut.
(b) Use the corners on the coupling nut between the flats on mating union to gage the
amount that coupling nut will have to move.
H-4
