Torque Data - Maintenance Practices; General - Cessna 172 Series 1996 Maintenance Manual

CESSNA AIRCRAFT COMPANY
MODEL 172
MAINTENANCE MANUAL
TORQUE DATA - MAINTENANCE PRACTICES
1.
General
A.
To ensure security of installation and prevent over stressing of components during installation, the
torque values outlined in this section and other applicable chapters of this manual should be used
during installation and repair of components.
B. The torque value tables, listed in this section, are standard torque values for the nut and bolt
combinations shown. If a component requires special torque values, those values will be listed in the
applicable maintenance practices section.
C. Torque is typically applied and measured using a torque wrench.
Different adapters, used in
conjunction with the torque wrench, may produce an actual torque to the nut or bolt which is different
from the torque reading. Figure 201 is provided to help calculate actual torque in relation to specific
adapters used with the torque wrench.
D.
Free Running Torque Value.
(1) Free running torque value is the torque value required to rotate a nut on a threaded shaft, without
tightening. Free running torque value does not represent the torque values listed in the tables
of this section. Torque values listed in the tables represent the torque values above free running
torque.
NOTE:
EXAMPLE: If final torque required is to be 150 inch-pounds and the free running
torque is 25 inch-pounds, then the free running torque must be added to the required
torque to achieve final torque of 150 + 25 =175 inch-pounds.
(2) Breakaway torque value is the value of torque required to start a nut rotating on a thread shaft,
and does not represent free running torque value. It should be noted that on some installations
the breakaway torque value cannot be measured.
E. General Torquing Notes.
(1) These requirements do not apply to threaded parts used for adjustment, such as turnbuckles
and rod ends.
(2) Torque values shown are for clean, non lubricated parts. Threads should be free of dust, metal
filings, etc. Lubricants, other than that on the nut as purchased, should not be used on any bolt
installation unless specified.
(3)
Assembly of threaded fasteners, such as bolts, screws and nuts, should conform to torque values
shown in Table 201.
(4) When necessary to tighten from the bolt head, increase maximum torque value by an amount
equal to shank friction. Measure shank friction with a torque wrench.
(5) Sheet metal screws should be tightened firmly, but not to a specific torque value.
(6) Countersunk washers used with close tolerance bolts must be installed correctly to ensure proper
torquing (refer to Figure 202).
(7) For Hi-Lok fasteners used with MS21042 self-locking nuts, fastener and nut should be lubricated
prior to tightening.
(8) Tighten accessible nuts to torque values per Table 201. Screws attached to nutplates, or screws
with threads not listed in Table 201 should be tightened firmly, but not to a specific torque value.
Screws used with dimpled washers should not be drawn tight enough to eliminate the washer
crown.
(9) Table 201 is not applicable to bolts, nuts and screws used in control systems or installations
where the required torque would cause binding, or would interfere with proper operation of parts.
On these installations, the assembly should be firm but not binding.
(10) Castellated Nuts.
(a) Self-locking and non self-locking castellated nuts, except MS17826, require cotter pins and
should be tightened to the minimum torque value shown in Table 201. The torque may be
increased to install the cotter pin, but this increase must not exceed the alternate torque
values.
(b)
MS17826 self-locking, castellated nuts shall be torqued per Table 201.
20-11-00
Page 201
Aug 18/2001