Recommended tightening torque and preload for metric bolts, by size and property class.
75% is a common target for a structural friction-grip or slip-critical joint.
Proof load
103.6 kN
Target preload
77.7 kN
Tightening torque
248.7 N·m
Nut factor K accounts for thread and bearing friction — it varies with lubrication, coating and condition, so treat this as a starting figure and confirm against the bolt manufacturer's data or a calibrated torque wrench check for a critical connection.