STANDARD BOLT & NUT TIGHTENING TORQUE
Standard bolt and nut tightening torques are not indicated.
Judge the standard tightening torque as shown below.
1. For tightening torque of hexagon head bolt, welded bolt and stud bolt with the standard bearing surface, identify
bolt class based on the below chart and then determine using the tightening torque table.
2. For tightening torque of hexagon flange bolts, identify bolt class based on the below chart and then determine
using the tightening torque table.
3. For tightening torque of nuts, check the mating bolt and use the method 1.
BOLT STRENGTH CLASS IDENTIFICATION METHOD
Identification by Bolt Shape
Shape and class Class
Hexagon head bolt
Bolt head No.
4 = 4T
5 = 5T
6 = 6T
7 = 7T
8 = 8T
No mark 4T
Two protruding lines 5T
Three protruding lines 7T
Four protruding lines 8T
Welded bolt 4T
Stud bolt
No mark 4T
Grooved 6T
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