Hex Bolt & Hex Cap Screw Dimensions

HEX BOLT

HEX CAP SCREW

ASME B18.2.1 (inch) and ISO 4014 / 4017 (metric) · basic dimensions

Inch, ASME B18.2.1 (in)

Size

Across flats

Cap screw head height

Hex bolt head height

Cap-screw LT (L 6 in or less)

1/4

7/16

5/32

11/64

3/4

5/16

1/2

13/64

7/32

7/8

3/8

9/16

15/64

1/4

1

7/16

5/8

9/32

19/64

1-1/8

1/2

3/4

5/16

11/32

1-1/4

9/16

13/16

23/64

-

1-3/8

5/8

15/16

25/64

27/64

1-1/2

3/4

1-1/8

15/32

1/2

1-3/4

7/8

1-5/16

35/64

37/64

2

1

1-1/2

39/64

43/64

2-1/4

1-1/4

1-7/8

25/32

27/32

2-3/4

1-1/2

2-1/4

15/16

1

3-1/4

Metric, ISO 4014 (bolt) / ISO 4017 (screw), mm

Size

Across flats s (ISO)

DIN 931 / 933 s

Head height k

M6

10

10

4

M8

13

13

5.3

M10

16

17

6.4

M12

18

19

7.5

M16

24

24

10

M20

30

30

12.5

M24

36

36

15

Cap-screw thread length LT: 2D + 1/4 in up to 6 in long, 2D + 1/2 in over 6 in. Hex bolts use their own thread-length rule. Basic values; see the standards for tolerances.

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