NCF
14
TECHNICAL ENCLOSURES
Tightening torques for nuts and bolts
The tightening torques M given in the table are applicable in the following conditions:
•
Hexagonal head UNI 5737 type screws, cylindrical head UNI 5931 and UNI 6107 type screws, in normal con-
ditions in which they are supplied.
•
Tightening torques must be applied slowly using a torque wrench.
While maintaining the same pre-load values, tightening torques must be modified as described below in the
following cases:
•
Increased by 5% for wide-head UNI 5712 screws.
•
Reduced by 10% for zinc plated oiled screws.
•
Reduced by 20% for phosphor coated oiled screws.
•
Reduced by 10% if the screw is tightened with an impulse tightener.
Tightening torques M for bolts with ISO metric thread
d x pitch (mm)
S r (mm²)
8.8
10.9
12.9
M (Nm)
M (Nm)
M (Nm)
6 x 1
20,1
10,4
15,3
17,9
7 x 1
28,9
17,2
25
30
8 x 1,25
36,6
25
37
44
10 x 1,5
58
50
73
86
12 x 1,75
84,3
86
127
148
14 x 2
115
137
201
235
16 x 2
157
214
314
368
18 x 2,5
192
306
435
509
20 x 2,5
245
432
615
719
22 x 2,5
303
592
843
987
24 x 3
353
744
1060
1240
27 x 3
459
1100
1570
1840
30 x 3,5
561
1500
2130
2500
