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
M5 7.0 7.8 10.0 11.7
M6 11.8 13.3 17.0 19.9
M8 28.8 32.3 41.3 48.3
M10 57.3 64.1 81.8 95.7
M12 99.8 112 143 167
M16 248 277 354 413
M20 500   690 809
M24 865   1195 1395
M30 1719   2377 2774

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.

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