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•
Thread diameter and appropriate tightening torque
kgf
cm
•
3000
(2604 in-lbs.)
2500
(2170 in-lbs.)
2000
(1736 in-lbs.)
1500
(1302 in-lbs.)
1000
(868 in-lbs.)
500
(434 in-lbs.)
0
7-2-3. Bolt Tightening torque characteristics
Fig. 4 shows relationships between time and tightening torque for individual bolt types and sizes. While the data
are useful for handy reference, actual tightening torque will vary depending on tightening conditions and other
variables. For details, please refer to Para. 8-3, "Tightening Torque Variation".
(Note)
•
The term "tightening time" indicates the impact time after the lower surface of the bolt has come in contact with
the material into which it is being tightened.
•
In the tightening conditions shown in Fig. 4, the screws are being tightened directly into a steel plate;
accordingly, the torque goes up very abruptly in comparison with ordinary bolt tightening conditions.
Bolt
Nut
M8 x 30
kgf
cm
•
N
m
•
(5/16" x 1-3/16")
(in-lbs.)
160
1600
(1389)
140
1400
(1215)
120
1200
(1042)
High-strength bolt
100
1000
(868)
80
800
(694)
60
600
(521)
40
400
(347)
Ordinary bolt
20
200
(174)
0
0
0
1
Tightening time: sec.
(Steel plate thickness
t= 3/8" (10 mm))
N
m
•
300
250
200
150
100
50
0
0
6
8
(1/4")
(5/16")
* The following bolts were utilized:
Ordinary bolt; strength grade 4.8
High-strength bolt; strengh grade 12.9
kgf
cm
•
(in-lbs.)
1600
(1389)
1400
(1215)
1200
(1042)
1000
(868)
800
(694)
600
(521)
400
(347)
200
(174)
0
2
3 (sec.)
10
12
(15/32")
(3/8")
Thread diameter
Fig. 3
Strength grade is read as follows:
4.8
M10 x 30
N
m
•
(3/8" x 1-3/16")
160
High-strength bolt
140
120
100
80
60
Ordinary bolt
40
20
0
0
2
1
3 (sec.)
Tightening time: sec.
(Steel plate thickness
t= 3/8" (10 mm))
Fig. 4
--- 9 ---
Strength grade 12.9
(high-strength bolt)
Strength grade 8.8
(high-strength bolt)
Strength grade 6.8
(ordinary bolt)
Strength grade 4.8
(ordinary bolt)
14
16
mm
(9/16")
(5/8")
Yield point or durable force:
(45,500 psi)
Tensile strength of the bolt:
(56,900 psi)
kgf
cm
•
N
m
•
(15/32" x 1-3/4")
(in-lbs.)
160
1600
(1389)
High-strength bolt
140
1400
(1215)
120
1200
(1042)
100
1000
(868)
80
800
(694)
Ordinary bolt
60
600
(521)
40
400
(347)
20
200
(174)
0
0
0
1
Tightening time: sec.
(Steel plate thickness
t= 1" (25 mm))
M12 x 45
2
3 (sec.)
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