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Reference values for tightening torques

The tightening torque required for an individual screw connection task can be taken from Table 6 as a reference value depending on nominal diameter and friction coefficient.

Tab. 14: Reference values for tightening torques for screws according to DIN EN ISO 3506

 

Friction coefficient

µtotal 0.10

 

Pretensioning forces Fvmax. [kN]

 

Tightening torque MA [Nm]

50

70

80

50

70

80

M 3

0.9

1

1.2

0.85

1

1.3

M 4

1.08

2.97

3.96

0.8

1.7

2.3

M 5

2.26

4.85

6.47

1.6

3.4

4.6

M 6

3.2

6.85

9.13

2.8

5.9

8

M 8

5.86

12.6

16.7

6.8

14.5

19.3

M 10

9.32

20

26.6

13.7

30

39.4

M 12

13.6

29.1

38.8

23.6

50

67

M 14

18.7

40

53.3

37.1

79

106

M 16

25.7

55

73.3

56

121

161

M 18

32.2

69

92

81

174

232

M 20

41.3

88.6

118.1

114

224

325

M 22

50

107

143

148

318

424

M 24

58

142

165

187

400

534

M 27

75

 

 

275

 

 

M 30

91

 

 

374

 

 

M 33

114

 

 

506

 

 

M 36

135

 

 

651

 

 

M 39

162

 

 

842

 

 


  

 

Friction coefficient

µtotal 0.40

 

Pretensioning forces Fvmax. [kN]

 

Tightening torque MA [Nm]

50

70

80

50

70

80

M 4

0.74

1.60

2.13

1.6

3.3

4.4

M 5

1.22

2.62

3.5

3.2

6.6

8.8

M 6

1.73

3.7

4.93

5.3

11.3

15.0

M 8

3.17

6.80

9.10

12.9

27.6

36.8

M 10

5.05

10.80

14.40

26.2

56.0

75.0

M 12

7.38

15.8

21.10

44.6

96.0

128.0

M 14

10.1

21.70

26.0

71.0

152.0

204.0

M 16

20.9

44.90

59.80

110

237

316

M 18

17.5

37.50

50.10

156

334

447

M 20

22.6

48.4

64.6

223

479

639

M 22

28.3

 

 

303

 

 

M 24

32.6

 

 

385

 

 

M 27

41.5

 

 

548

 

 

M 30

50.3

 

 

740

 

 

M 33

63.0

 

 

1013

 

 

M 36

74.0

 

 

1296

 

 

M 39

89.0

 

 

1694

 

 


Friction coefficients µG and µK according to DIN 267 Part 11

 

Tab. 15: Friction coefficients µG and µK for screws made from stainless steel and anti-corrosion steel


 

Screw made from

 

Nut made from

 

µtotal When lubricated

 

No lubrication

MoS2

paste

A 2 or A 4

A 2 or A 4

0.23 - 0.5

0.10 - 0.20

A 2 or A 4

AIMgSi

0.28 - 0.35

0.08 - 0.16

  

Friction coefficients µtotal require the same friction value in the thread and under the head / nut support.


Tab. 16: Friction coefficients µG and µK for screws and nuts made from stainless steel and anti-corrosion steel

 

 

Screw made from

 

Nut made from

 

Lubricant

 

Resilience of connection

 

Friction coefficient

 

in thread

 

under head

 

in thread

µG

under head

µK

 

 

 

 

 

 

 

 

 

A 2

 

 

 

 

 

 

A 2

 

none

 

none

 

 

 

very high

0.26 to

0.50

0.35 to

0.50

Special lubricant (chloroparaffin base)

0.12 to

0.23

0.08 to

0.12

 

Anticorrosive grease

0.26 to

0.45

0.25 to

0.35

 

none

 

none

 

 

low

0.23 to

0.35

0.12 to

0.16

Special lubricant (chloroparaffin base)

0.10 to

0.16

0.08 to

0.12

 

 

AIMgSi

 

none

 

 

 

very high

0.32 to

0.43

0.08 to

0.11

Special lubricant (chloroparaffin base)

0.28 to

0.35

0.08 to

0.11

Hex nuts with a clamping part made from stainless steels tend to seize because of the high thread flank pressure as the thread moulds into the clamping part. Using a friction-reducing agent can remedy the situation. But this should be taken into account accordingly for friction values.