7 Reference information
7.4. Screw joints
3913HAC026876-001 Revision: C
© Copyright 2006-2008 ABB. All rights reserved.
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 pneumatical 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.
The table below specifies the recommended standard tightening torque for Molycote-
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
Dimension
Tightening torque (Nm)
Class 10.9, Molycote-lubricated
Tightening torque (Nm)
Class 12.9, Molycote-lubricated
M8 28 35
M10 55 70
M12 96 120
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