-8-
(3) Tightening torque characteristics
The graph below shows the relationship between tightening time and tightening torque according to
types of bolts. The data below are intended for reference purposes only because actual tightening
torque may vary depending on tightening conditions and other factors. For details, please refer to “3.
Tightening torque variation” (page 12).
NOTE:
•
The term "tightening time" means the impact time after the lower surface of the bolt comes in contact with
the material to be tightened.
•
Each bolt is directly tightened into a steel plate under the following tightening conditions. Accordingly, the
torque goes up very abruptly in comparison with the actual bolt tightening conditions.
Bolt
Nut
St
eel plate thickness t
Following bolts were used.
Ordinary bolt: Strength grade 4.8
High-strength bolt: Strength grade 12.9
Strength grade is read as follows.
4.8
Yield point or durable force
(45,500 psi)
Tensile strength of bolt
(56,900 psi)