Holes and Counterbore Sizes

 

Metric SHCS Hole & Counterbore Sizes

 

Nominal Screw Size

Clearance Hole Dia. mm

Counterbore Dia. mm

Countersink Dia. mm

Tapping Drill mm

 

Close

Normal

 

 

ISO

M Fine

M3

3.4

3.7

6.5

3.6

0.5

-

M4

4.4

4.8

8.25

4.7

0.7

-

M5

5.4

5.8

9.75

5.7

4.2

-

M6

6.4

6.8

11.25

6.8

5.0

-

M8

8.4

8.8

14.25

9.2

6.8

7.0

M10

10.5

10.8

17.25

11.2

8.5

8.8

M12

12.5

12.8

19.25

14.2

10.2

10.5

M14

14.5

14.75

22.25

16.2

12.0

12.5

M16

16.5

16.75

25.5

18.2

14.0

14.5

M20

20.5

20.75

31.5

22.4

17.5

18.5

M24

24.5

24.75

37.5

26.4

21.0

22.0

M30

30.75

31.75

47.5

33.4

26.5

-

 

 

Imperial SHCS Hole & Counterbore Sizes

 

Nominal Screw Size

Clearance Hole Dia. mm

Counterbore Dia. mm

Countersink Dia. mm

Tapping Drill mm

 

Close

Normal

 

 

UNF

UNC

8

4.6

5.0

8.0

4.8

3.5

3.4

10

5.2

5.6

9.5

5.5

4.1

3.8

1/4"

6.8

7.2

11.0

7.0

5.5

5.1

5/16"

8.4

8.8

13.5

8.8

6.9

6.6

3/8"

10.0

10.4

16.0

10.5

8.5

8.0

7/16"

11.5

12.0

18.0

12.2

9.8

9.4

1/2"

13.0

13.5

20.5

14.0

11.5

10.8

5/8"

16.2

16.8

25.5

17.5

14.5

13.5

3/4"

19.5

19.8

30.0

21.0

17.5

16.5

7/8"

22.8

23.0

35.0

24.5

20.5

19.5

1"

25.8

26.2

41.0

28.0

23.5

22.0

1 1/4"

32.6

33.4

50

35

29.5

28.0

 

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