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How to determine the Thread Length of your Hex Cap Screws (Imperial/Metric) and Structural Bolts

Posted by Guillaume Lachapelle on

Looking for the length of the bolt that would be the best for your project? We are here to help.

 

Imperial (Inch)  Standard Thread Length Chart for Bolts

Diameter 

Nominal Thread Length 

Nominal Thread Length 

A325 & A490 

(Inch)

 6" and Less

Greater Than 6"

Thread Length

1/4"

0.75

1

-

5/16"

0.875

1.125

-

3/8"

1

1.25

-

7/16"

1.125

1.375

-

1/2"

1.25

1.5

1

9/16"

1.375

1.625

-

5/8"

1.5

1.75

1.25

3/4"

1.75

2

1.375

7/8"

2

2.25

1.5

1"

2.25

2.5

1.75

1-1/8"

2.5

2.75

2

1-1/4"

2.75

3

2

1-3/8"

3

3.25

2.25

1-1/2"

3.25

3.5

2.25

1-3/4"

3.75

4

-

2"

4.25

4.5

-

2-1/4"

4.75

5

-

2-1/2"

5.25

5.5

-

2-3/4"

5.75

6

-

3"

6.25

6.5

-

3-1/4"

6.75

7

-

3-1/2"

7.25

7.5

-

3-3/4"

7.75

8

-

4"

8.25

8.5

-

Metric (mm) Standard Thread Length Chart For Bolts

Bolt Diameter

Standard Thead Length (mm) *

(mm)

Bolts 125mm and shorter

Bolts >125mm and <125 

Bolts >200mm

M3

12

-

-

M4

14

-

-

M5

16

22

35

M6

18

24

37

M7

20

26

39

M8

22

28

41

M10

26

32

45

M12

30

36

49

M14

34

40

53

M16

38

44

57

M18

42

48

61

M20

46

52

65

M24

54

60

73

M30

66

72

85

M36

78

84

97

M42

90

96

109

M48

102

108

121

M56

-

124

137

M64

-

140

153

M72

-

156

169

M80

-

172

185

M90

-

192

205

M100

-

 212

225

*Please note: Per norm ANSI/ASME B18.2.3.5M-1989

 

 

Here are the maths you will need to do to determine the thread length you will get on standard Hex cap screws.

HOW TO CALCULATE HEX CAP SCREW/HEX BOLT THREAD LENGTH IMPERIAL/METRIC
 

Tap bolts with full thread length might also be available in Imperial and Metric sizes.

Different type of Bolts : EG: Structural Bolts, Carriage Bolts and Lag Bolts will also have different rules for their respective thread length.

When in doubt , contact us at Boulonseclair@boulonseclair.com our team of professionnal will be more than happy to help you.


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