(3)
Usually, you will use the torque values that are specified in this procedure.
(a)
When a installation procedure gives you a torque value, use that torque value.
(b)
But when an installation procedure tells you to tighten a bolt, but does not give a torque value, refer to 20-50-11/201.
(4)
Make sure that you apply the torque accurately.
(a)
A torque of one pound-inch is a force of one pound applied to a lever at a distance of one inch from the of the fastener (whereas one N.m is the force of one Newton you apply to a lever one meter in length).
(b)
To calculate the torque, you multiply the force that you apply in pounds (Newtons) by the distance of the force from the axis of the fastener in inches (meters).
(c)
The specified torque is the best value for the fastener and the part that it holds. The specified torque will cause the fastener to hold the part tightly but will not break the fastener or the part.
NOTE: Torque values are shown in pound-inches (N.m) to
____ identify it from a force you apply over a distance (work), which is shown as inch-pounds or joules (J).
B. Procedure
S 912-001-C00
(1) Definitions
(a) Terms about the procedure to tighten are: 1) BOLT - A male part that has threads. 2) BREAKAWAY TORQUE - The maximum torque that you must apply
before you make the fastener move. 3) GROSS TORQUE - The torque that the gage on the torque wrench shows. 4) INSTALLED NUT - A nut is referred to as an installed nut when these conditions occur:
-
The nut has the specified torque.
-
The chamfer and 1-1/2 threads of the bolt show above the nut, or the chamfer and 1-1/2 threads of the bolt show above the lock device.
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ALL ú ú C01 Page 201 ú Jul 15/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
5) MAXIMUM INSTALLATION TORQUE - The highest value to get as the nut is initially installed and sized ("opened up" or "worn in") by the bolt.
6) MINIMUM PREVAILING TORQUE - The minimum value you get while the nut or bolt moves from the end of the first revolution to the end of the second revolution (during the removal of the nut from the bolt or the bolt from a threaded hole).
7) REMOVED NUT - A self-locking nut is removed when you remove the lock part from the bolt. (It is not necessary for the nut to be removed from the bolt.)
8) RUN-ON TORQUE - The torque that is necessary to turn a nut or bolt before it is fully engaged (an axial tightening effect on the bolt or spacing elements).
9) SEATED NUT or BOLT - A nut or bolt is engaged when its bearing surface touches a spacer. An axial load is put on the bolt when you apply a specified seating torque or compressive force. When you get a measured extention of the bolt.
10) SEATING TORQUE - The torque you apply to a specified compressive force to the spacing elements. An axial load or an extention force to a bolt (after the bearing surfaces of the bolt and nut touch the spacing elements).
11) SPACER, SPACING ELEMENTS - All of the parts (regardless of function, size, shape or material) are held together by one or more fasteners that have threads.
12) UNSEATED NUT or BOLT - A nut or bolt is unseated when it is removed a minimum of one turn from the seated position. When you remove all the axial load from the bolt.
13) UNSEATING TORQUE - The torque that is necessary to unseat the bearing surface of a nut or bolt from a spacer. (When you remove all the axial load from the bolt).
S 912-003-C00
(2) Procedure to Tighten the Parts.
(a)
When you tighten the nuts, you must apply the specified torque values. 1) These torque values are given to make sure of the best
procedure to tighten the parts for safety functions.
(b)
On flanges with a large number of bolts and nuts, tighten the pairs of bolts that are opposite to each other.
(c)
On the same flanges, it is recommended to continue to a last check, clockwise. 1) Make sure all the nuts are tight to the specified torque
values.
(d)
Tighten at a constant rate until you get the specified torque.
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