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1.4
The values specified in the table apply for screws:
black oiled
l
with surface protection A4C
l
with surface protection DACROMET
l
i
Note
The difference between Withworth and UNF/UNC threads is the fact that UNF and UNC threads have 60° flanks,
as the metric ISO-thread, whereas Withworth has a flank of only 55°.
DACROMET is a surface protection that mainly consists of zinc and aluminium in a chromium oxide matrix. DAC-
ROMETIZATION provides excellent corrosion protection for metal surfaces by applying a mineral coating with
metallic-silver appearance.
Tightening torques for screws with UNC thread,
Coarse Thread
Screw dimension
1/4" - 20
5/16" - 18
3/8" - 16
7/16" - 14
1/2" - 13
9/16" - 12
5/8" - 11
3/4" - 10
7/8" - 9
1" - 8
1 1/8" - 7
1 1/4" - 7
1 3/8" - 6
1 1/2" - 6
μ
*
Coefficient of friction
tot. = 0,14
Tightening torques for screws with UNF thread,
Unified Fine Thread
Screw dimension
1/4" - 28
5/16" - 24
3/8" - 24
7/16" - 20
1/2" - 20
9/16" - 18
5/8" - 18
3/4" - 16
7/8" -14
32
*
UNC Unified Coarse Thread Series, American Unified
Tightening torques Nm
8.8
11
23
39
62
96
140
195
345
560
850
1200
1700
2200
3000
*
UNF Unified National Fine Thread Series, American
Tightening torques Nm
8.8
13
25
45
70
110
155
220
385
620
BOMAG
Tightening torques
10.9
15
32
55
87
135
200
275
485
770
1200
1700
2400
3100
4200
10.9
18
35
63
100
155
220
310
540
870
12.9
19
39
66
105
160
235
330
580
940
1450
2000
2900
3700
5100
12.9
22
42
76
120
185
260
370
650
1050
008 916 89
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