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1. STANDARD TIGHTENING TORQUE SPECIFICATION
Tabulated below are the tightening torques for commercial bolts and nuts according to their metric threads and
grades.
THREAD
M.5
M.6
M.8
M.10
M.12
M.14
M.16
M.18
M.20
M.22
M.24
M.27
M.33
Table 1 – Tightening torques for the fasteners' different threads and grades
Screw tightening torques outside this standard specification are listed in documents IM-F-C-00-002e and IM-F-C-
00-004e for diesel and dual-fuel engines and IM-G-C-00-001e for gas and ethanol engines.
2. CALCULATING THE SCREW PRE-STRESSING FORCE ACCORDING TO THE
APPLIED TIGHTENING TORQUE
The screw tightening torque is useful for two purposes:
-
To overcome friction between contact areas, whether between screw and nut threads or between screw head
and bearing surface.
-
To apply a pre-stressing force to the fastener.
The amount of tightening torque usable for applying the pre-stressing force varies depending on the coefficient of
friction to overcome. Therefore, even though the same tightening torque is applied to two identical screws, the
pre-stressing force can vary if the coefficient of friction is different in both instances. The lower the coefficient, the
lower the effort needed to overcome friction and consequently, the pre-stressing force will be greater.
Torques table 1 has been calculated with a coefficient of friction standard for steel μ=0.14. For other coatings,
look at Table 2.
PRODUCT INFORMATION
IM-C-C-00-002e
TIGHTENING TORQUES FOR COMMERCIAL BOLTS & NUTS
8.8
N.m
Ft.lb
6
4.4
11
8
25
18
47
35
78
58
120
86
180
133
250
184
330
243
430
317
560
413
710
524
1110
819
INDEX
B
GRADE
10.9
N.m
Ft.lb
9
6,6
15
11
34
25
65
48
113
83
175
129
260
192
360
266
470
347
600
443
790
583
1060
782
1540
1136
2.1.37
DATE
Dep.2
February 2012
O&M_2.002211.810_A_10_2016
12.9
N.m
Ft.lb
11
8.1
18
13.3
43
32
83
61
140
103
210
155
310
229
430
317
560
413
720
531
950
701
1180
870
1730
1276
1/3
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