Tightening Torque - Hitachi wh 14daf2 Technical Data And Service Manual

7-2. Tightening Torque

7-2-1. Screw diameter and appropriate tightening torque
Generally speaking, the appropriate tightening torque for a screw can be determined by the strength grade of the
screw and the material tightened. Tables 1 and 2, and Fig. 4 below list data relative to the strength grade of
various screws and the appropriate tightening torque. For further reference, appropriate tightening torque is
calculated with the following formula. Study and use this formula for accurate selection of tightening torque.
T=k d p
• •
T: Appropriate tightening torque (kgf
d: Nominal diameter for the screw (mm)
p: Recommended axial tightening force to be applied to the screw (kgf)
p=rated axial stress (kgf/cm
K: Torque coefficient (0.17)
Strength grade and rated axial stress of threads
Strength grade
Rated axial stress (kgf/mm
Material
Heat treatment
Diameter and effective sectional areas of threads
Kind of thread (x pitch)
Effective sectional area of
thread (mm 2 )
Thread diameter and appropriate tightening torque
.
(117.6 N m, 86 ft-lbs.)
.
(98 N m, 72 ft-lbs.)
.
(78.4 N m, 58 ft-lbs.)
.
(58.8 N m, 43 ft-lbs.)
.
(39.2 N m, 29 ft-lbs.)
.
(19.6 N m, 14 ft-lbs.)
cm)
•
2 ) x 0.8 x effective sectional area of the thread (mm
4.8
2 )
29.1
Mild steel
M5 x 0.8 mm M6 x 1 mm
(3/16") (1/4")
14.2
.
(kgf cm)
1200
1000
800
600
400
200
0
0 5 6
(3/16") (1/4")
Table 1
6.8
43.7
None
Table 2
M8 x 1.25 mm
(5/16")
20.1 36.6
8 10 12
(5/16") (3/8") (15/32")
Thread diameter
Fig. 4
--- 8 ---
2 )
8.8
58.2
Alloy steel including Ni, Mn, Cr, etc.
Processed-hard material
M10 x 1.5 mm M12 x 1.75 mm
(3/18") (15/32")
58.0 84.3
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
mm
(9/16")
12.9
95
M14 x 2 mm
(9/16")
115