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(2) Bolt tightening torque characteristics
The graphs below show 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. For details, please refer to "Tightening torque
variation."
NOTE:
•
The term "tightening time" means the impact time after the lower surface of the bolt comes in contact
with the material into which it is being tightened.
• Each bolt is tightened directly into a steel plate under the following tightening conditions.
Accordingly, the torque goes up very abruptly in comparison with the ordinary bolt tightening
conditions.
* The 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 the bolt:
(56,900 psi)