PRODUCT INFORMATION
INDEX
DATE
Dep.2
IM-C-C-00-002e B
February 2012
TIGHTENING TORQUES FOR COMMERCIAL BOLTS & NUTS
1/3
1. STANDARD TIGHTENING TORQUE SPECIFICATION
Tabulated below are the tightening torques for commercial bolts and nuts according to their metric threads and
grades.
THREAD
GRADE
8.8 10.9 12.9
N.m Ft.lb N.m Ft.lb N.m Ft.lb
M.5
6 4.4 9 6,6 11 8.1
M.6
11 8 15 11 18 13.3
M.8
25 18 34 25 43 32
M.10
47 35 65 48 83 61
M.12
78 58 113 83 140 103
M.14
120 86 175 129 210 155
M.16
180 133 260 192 310 229
M.18
250 184 360 266 430 317
M.20
330 243 470 347 560 413
M.22
430 317 600 443 720 531
M.24
560 413 790 583 950 701
M.27
710 524 1060 782 1180 870
M.33
1110 819 1540 1136 1730 1276
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.
2.1.37
O&M_2.002211.810_A_10_2016
