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Metric Fasteners

Machine Screws
ISO metric machine screws are limited
to four different head shapes: countersunk, raised
countersunk, panhead, and cheesehead.

All head dimensions are directly related to the basic screw
diameter as follows:

Size

Minimum Length (mm)

M1.6

15

M2

16

M2.5

18

M3

19

M4

22

M5

25

M6

28

M8

34

M10

40

M12

46

M16

58

M20

70

Socket Screws
ISO metric hexagon socket screws are
limited to two different head shapes: cap screw, and
countersunk socket screw.

All head dimensions are directly related to the basic screw
diameter as follows:

Size

Minimum Length (mm)

M3

3

M4

10

M5

12

M6

16

M8

20

M10

25

M12

30

Nuts and Washers
The nut and washer dimensions are related
to the basic screw diameter as follows:

Bolts
Bolt head dimensions are related to their diameter as
follows: