Metric Bolt Tightening Torques
Maximum Tightening Torques for Coarse Threaded Metric Bolts
Property classes (grades) are defined by ISO 898 (Mechanical properties of fasteners made of carbon steel and alloy steel). This table shows values for threads that have been lightly oiled and the tension is 85% of the proof load.
|Size (mm)||Recommended Maximum Tightening Torque (Nm)|
|Grade 8.8||Grade 9.8||Grade 10.9||Grade 12.9|
These values should only be used when the machine manufacturer has not provided their own. Fine pitch bolts also have different torque levels generally specified in the manufacturer’s documentation.