BA 5200 EN 08/2010
6.20
Screwconnection classes, tightening torques and initial tensioning forces
6.20.1
Screwconnection classes
The specified screw connections are to be fastened applying the tightening torques specified in the table
below.
Table 10:
Screwconnection classes
Screwconnection
class
Distribution
of emitted torque
on the tool
Tightening procedure
(Usually the tightening processes lie within the stated
tool distribution)
C
± 5 % up to ± 10 %
‐ Hydraulic tightening with mechanical screwdriver
Torquecontrolled tightening with torque wrench
or signalemitting torque wrench
Tightening with precision mechanical screwdriver
with dynamic torque measuring
D
± 10 % up to ± 20 %
‐ Torquecontrolled tightening with mechanical screwdriver
E
± 20 % up to ± 50 %
‐ Tightening with pulse screwdriver or impact wrench
without adjustment checking device
Tightening by hand, using a spanner without torque
measuring device
Foundation bolts, hub bolts and bearingcover bolts must always be tightened in
accordance with screwconnection class "C"!
6.20.2
Tightening torques and initial tensioning forces
The tightening torques apply to friction coefficients of μ
total
= 0.14. The friction
coefficient μ
total
= 0.14 applies here to lightly oiled steel bolts, blackannealed or phosphatised
and dry, cut mating threads in steel or cast iron. Lubricants which alter the friction coefficient
must not be used and may overload the screw connection.
Table 11:
Initial tensioning forces and tightening torques for screw connections of strength classes
8.8;
10.9; 12.9
with a common friction coefficient of
μ
total
= 0.14
Nominal
thread
diameter
Strength
class of the
bolt
Initial tensioning force
for screwconnection classes
from table 10
Tightening torque
for screwconnection classes
from table 10
C
D
E
C
D
E
d
mm
F
M min.
N
M
A
Nm
M10
8.8
18000
11500
7200
44.6
38.4
34.3
10.9
26400
16900
10600
65.4
56.4
50.4
12.9
30900
19800
12400
76.5
66.0
58.9
M12
8.8
26300
16800
10500
76.7
66.1
59.0
10.9
38600
24700
15400
113
97.1
86.6
12.9
45100
28900
18100
132
114
101
M16
8.8
49300
31600
19800
186
160
143
10.9
72500
46400
29000
273
235
210
12.9
85000
54400
34000
320
276
246
M20
8.8
77000
49200
30800
364
313
280
10.9
110000
70400
44000
520
450
400
12.9
129000
82400
51500
609
525
468