7 Reference information
7.4. Screw joints
3HAC026876-001 Revision: F
406
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Tightening torque
Before tightening any screw, note the following:
•
Determine whether a standard tightening torque or special torque is to be applied.
The standard torques are specified in the tables below. Any special torques are
specified in the Repair, Maintenance or Installation procedure descriptions. Any
special torque specified overrides the standard torque!
•
Use the correct tightening torque for each type of screw joint.
•
Only use correctly calibrated torque keys.
•
Always tighten the joint by hand, and never use pneumatic tools.
•
Use the correct tightening technique, that is do not jerk. Tighten the screw in a slow,
flowing motion.
•
Maximum allowed total deviation from the specified value is 10%!
The table below specifies the recommended standard tightening torque for oil-lubricated
screws with slotted or cross-recess head screws.
The table below specifies the recommended standard tightening torque for oil-lubricated
screws with Allen head screws.
Dimension
Tightening torque (Nm)
Class 4.8, oil-lubricated
M2.5
0.25
M3
0.5
M4
1.2
M5
2.5
M6
5.0
Dimension
Tightening torque
(Nm)
Class 8.8, oil-lubri-
cated
Tightening torque
(Nm)
Class 10.9, oil-lubri-
cated
Tightening torque
(Nm)
Class 12.9, oil-lubri-
cated
M5
6
-
-
M6
10
-
-
M8
24
34
40
M10
47
67
80
M12
82
115
140
M16
200
290
340
M24
725
960
1150
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