Hitachi WH 12DM2 Technical Data And Service Manual page 27

7-3-3. Bolt tightening torque characteristics
Figures. 6-1 and 6-2 show 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 Figs. 6-1 and 6-2, 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
•
Model WH 12DM2
kgf cm
N m
•
•
1000 100
High-strength bolt
80
800
600 60
40
400
Ordinary bolt
200 20
0
0
0
Tightening time: sec.
(Steel plate thickness
t = 10 mm)
•
Model WR 12DM2
N m
kgf cm
•
•
2000
200
1500
150
High-strength bolt
1000 100
50
500
Ordinary bolt
0
0
0
Tightening time: sec.
(Steel plate thickness
t = 10 mm)
* The following bolts were utilized:
Ordinary bolt; strength grade 4.8
High-strength bolt; strengh grade
kgf
•
1400
1200
M10 x 30
1000
800
600
400
200
3
1 2
kgf
M10 x 30
2000
1500
1000
1
2 3
12.9
N m
cm
•
M12 x 45
140
High-strength bolt
120
100
80
60
Ordinary bolt
40
20
0 0
0
1 2
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
Fig. 6-1
cm N m
• •
M12 x 45
200
High-strength bolt
150
100
500 50
Ordinary bolt
0
0
0 1
2
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
Fig. 6-2
--- 24 ---
Strength grade is read as follows:
4.8
Yield point or durable force:
(45,500 psi)
Tensile strength of the bolt:
(56,900 psi)
kgf cm N m
•
•
140
1400
High-strength bolt
120
1200
1000 100
800 80
600 60 Ordinary bolt
400 40
200
20
0 0
3
0
Tightening time: sec.
(Steel plate thickness
t = 25 mm))
N m
kgf cm
•
•
200
2000
150
1500
100
1000
50
500
0 0
0
3
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
M14 x 50
2 3
1
M14 x 50
High-strength bolt
Ordinary bolt
2 3
1