8 Reference information
8.4. Screw joints
4333HAC023082-001 Revision: E
© Copyright 2004-2008 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 description. Any special torque
specified overrides the standard value.
• 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, i.e. 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.
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
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