Nominal

Tapping hole size

Thread sleeve length (laps)

Metric  coarse thread

Min

Max

Drill

1D

1.5D

2D

2.5D

3D

M3-0.5

3.12

3.20

3.1

4

6 5/8

9 1/4

11 7/8

14 1/2

M4-0.7

4.17

4.30

4.2

3 7/8

6 3/8

8 7/8

11 3/8

13 7/8

M5-0.8

5.16

5.33

5.2

4 3/8

7 1/8

9 7/8

12 5/8

15 1/2

M6-1.0

6.25

6.42

6.3

4 1/4

7 1/8

10

12 7/8

15 3/4

M7-1.0

7.25

7.42

7.3

5 1/2

8 5/8

11 3/4

14 1/8

17 1/4

M8-1.25

8.31

8.52

8.4

4 5/8

7 3/8

10 1/4

13 1/8

16

M10-1.5

10.37

10.62

10.5

5

8

11

14

17

M12-1.75

12.43

12.73

12.5

5

8 1/4

11 3/8

14 1/2

17 3/4

M14-2.0

14.49

14.83

14.5

5 1/4

8 1/2

11 3/4

15

18 3/8

M16-2.0

16.49

16.83

16.5

6 1/8

9 7/8

13 1/2

17 1/4

21

M18-2.5

18.58

19.04

19.0

5 5/8

9

12 1/2

15 5/8

19

M20-2.5

20.58

21.04

21.0

6 3/8

10 1/8

14

17 3/8

21 1/8

M22-2.5

22.58

23.04

23.0

7 1/8

11 1/4

15 1/2

19

23 1/8

Metric  fine thread

Min

Max

Drill

1D

1.5D

2D

2.5D

3D

M8-1.0

8.25

8.42

8.3

6

9 5/8

13 1/8

16 1/2

20 1/8

M10-1.0

10.25

10.42

10.3

7 7/8

12 3/8

17

21

25 1/2

M10-1.25

10.31

10.52

10.4

5 7/8

9 1/2

13 1/8

16 3/4

20 3/8

M12-1.25

12.31

12.52

12.4

7 3/8

11 5/8

16

20 1/4

24 1/2

M12-1.5

12.37

12.62

12.5

6

9 1/2

13 1/8

17

20 3/4

M14-1.5

14.37

14.62

14.5

7

11 1/8

15 3/8

20

24 1/4

M16-1.5

16.37

16.62

16.5

8 1/2

13 3/8

18 1/8

22 3/4

27 5/8

M18-1.5

18.37

18.62

18.5

9 3/4

15 1/8

20 5/8

25 7/8

31 3/8

M20-1.5

20.37

20.62

20.5

10 3/8

16 1/8

22

28 7/8

35

Imperial  coarse thread

Min

Max

Drill

1D

1.5D

2D

2.5D

3D

U#4-40

2.95

3.07

3.0

2 3/4

4 3/4

6 3/4

8 7/8

10 7/8

U#5-40

3.25

3.38

3.3

3 1/4

5 1/2

7 3/4

10

12 1/4

U#6-32

3.66

3.81

3.7

2 3/4

4 3/4

6 7/8

8 7/8

10 7/8

U#8-32

4.32

4.47

4.4

3 1/2

6

8 3/8

10 3/4

13 1/4

U#10-24

5.05

5.21

5.1

2 7/8

5

7 1/8

9 1/4

11 3/4

U1/4-20

6.63

6.78

6.7

3 3/8

5 3/4

8

10 3/8

12 3/4

U5/16-18

8.33

8.48

8.4

4

6 5/8

9 1/4

11 7/8

14 5/8

U3/8-16

9.91

10.11

10.0

4 3/8

7 1/4

10

12 7/8

15 3/4

U7/16-14

11.51

11.76

11.6

4 1/2

7 3/8

10 1/4

13 1/8

16 1/8

U1/2-13

13.08

13.34

13.2

4 7/8

7 7/8

11

14 1/8

17 1/8

U9/16-12

14.68

14.94

14.8

5 1/8

8 1/4

11 1/2

14 3/4

17 7/8

U5/8-11

16.59

16.84

16.7

5 1/4

8 1/2

11 3/4

15

18 3/8

U3/4-10

19.84

20.09

20.0

5 7/8

9 3/8

13

16 1/2

20 1/8

U7/8-9

23.01

23.27

23.0

6 1/4

10

13 3/4

17 1/2

21 1/4

I mperial fine thread

Min

Max

Drill

1D

1.5D

2D

2.5D

3D

U#8-36

4.32

4.44

4.4

3 7/8

6 1/2

9 1/8

11 5/8

14 1/4

U#10-32

4.98

5.13

5.0

4 1/8

6 7/8

9 1/2

12 1/4

14 7/8

U1/4-28

6.53

6.71

6.6

5

8 1/4

11 3/8

14 1/2

17 5/8

U5/16-24

8.20

8.38

8.3

5 1/2

8 7/8

12 1/4

15 5/8

19

U3/8-24

9.78

9.96

9.8

6 7/8

11

15

19 1/8

23 1/8

U7/16-20

11.43

11.63

11.5

6 5/8

10 5/8

14 5/8

18 1/2

22 1/2

U1/2-20

13.03

13.26

13.1

7 7/8

12 3/8

16 7/8

21 3/8

25 7/8

U5/8-18

16.26

16.48

16.3

9

14 1/8

19 1/4

24 1/4

29 3/8

U3/4-16

19.43

19.68

19.5

9 3/4

15 1/8

20 5/8

26

31 1/2

Spark plug only

Min

Max

Drill

7.7L

10L

15L

20L

M14-1.25

14.27

14.40

14.30

4 5/8

6 1/2

9 3/4

13 1/8