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Whether you are tapping a thread or drilling a hole, you can find the correct thread size and tap drill you need to use here. We stock a massive range of taps and drills for your next job.

Metric Course Thread Drilling Chart

Thread Size Tap Drill (mm) Thread Size Tap Drill (mm) Thread Size Tap Drill (mm) Thread Size Tap Drill (mm)

M1 x 0.25

0.75

M3.5 x 0.6

2.90

M12 x 1.75

10.20

M36 x 4

32.00

M1.1 x 0.25

0.85

M4 x 0.7

3.30

M14 x 2

12.00

M39 x 4

35.00

M1.2 x 0.25

0.95

M4.5 x 0.75

3.70

M16 x 2

14.00

M42 x 4.5

37.50

M1.4 x 0.3

1.10

M5 x 0.8

4.20

M18 x 2.5

15.50

M45 x 4.5

40.50

M1.6 x 0.35

1.25

M6 x 1

5.00

M20 x 2.5

17.50

M48 x 5

43.00

M1.8 x 0.35

1.45

M7 x 1

6.00

M22 x 2.5

19.50

M52 x 5

47.00

M2 x 0.4

1.60

M8 x 1.25

6.80

M24 x 3

21.00

M56 x 5.5

50.50

M2.2 x 0.45

1.75

M9 x 1.25

7.80

M27 x 3

24.00

M60 x 5.5

54.50

M2.5 x 0.45

2.05

M10 x 1.5

8.50

M30 x 3.5

26.50

M64 x 6

58.00

M3 x 0.5

2.50

M11 x 1.5

9.50

M33 x 3.5

29.50

M68 x 6

62.00

Metric Fine Thread Drilling Chart

Thread Size Tap Drill (mm) Thread Size Tap Drill (mm) Thread Size Tap Drill (mm) Thread Size Tap Drill (mm)

M4 x 0.35

3.60

M10 x 0.75

9.25

M16 x 1

15.0

M24 x 1.5

22.5

M4 x 0.5

3.50

M10 x 1

9.0

M16 x 1.5

15.0

M24 x 2

22.0

M5 x 0.5

4.50

M10 x 1.25

8.8

M18 x 1

17.0

M26 x 1.5

24.5

M6 x .5

5.50

M11 x 1

10.0

M18 x 2

16.0

M27 x 1.5

25.5

M6 x .75

5.25

M12 x .75

11.25

M20 x 1

19.0

M27 x 2

25.0

M7 x .75

6.25

M12 x 1

11.0

M20 x 1.5

18.5

M28 x 1.5

26.5

M8 x .5

7.00

M12 x 1.5

10.5

M20 x 2

18.0

M30 x 1.5

28.5

M8 x .75

7.25

M14 x 1

13.0

M22 x 1

21.0

M30 x 2

28.0

M8 x 1

7.50

M14 x 1.25

12.8

M22 x 1.5

20.5

M33 x 2

31.0

M9 x 1

8.00

M14 x 1.5

12.5

M22 x 2

20.0

M36 x 3

33.0

Imperial

UNC

Unified National Coarse

Tap Size Drill Size
1/4-20NC #8
5/16-18NC F
3/8-16NC 5/16
7/16-14NC U
1/2-13NC 27/64
9/16-12NC 31/64
5/8-11NC 14mm
3/4-10NC 21/32
7/8-9NC 49/64
1-8NC 7/8
1 1/8-7NC 63/64
1 1/4-7NC 1-7/64
1 3/8-6NC 1-3/16
1 1/2-6NC 1-11/32

UNF

Unified National Fine

Tap Size Drill Size
1/4-28NF #3
5/16-24NF I
3/8-24NF Q
7/16-20NF W
1/2-20NF 29/64
9/16-18NF 33/64
5/8-18NF 37/64
3/4-16NF 11/16
7/8-14NF 13/16
1-12NF 29/32
1 1/8-12NF 1-3/64
1 1/4-12NF 1-11/64
1 3/8-12NF 1-19/64
1 1/2-12NF 1-27/64

NS

Tap Size Drill Size
5/32-32NS 1/8
5/32-36NS #30
3/16-24NS #26
3/16-32NS #22
7/32-24NS #16
7/32-32NS #12
1/4-32NS 7/32
1/4-40NS #1
5/16-32NS 9/32
11/16-16NS 5/8
1-14NS 15/16

NPT

National Pipe Taper 1:16

Tap Size Drill Size
1/8-27NPT R
1/4-18NPT 7/16
3/8-18NPT 15mm
1/2-14NPT 23/32
3/4-14NPT 59/64
1 x11-1/2NPT 1-5/32
1-1/4×11-1/2NPT 1-1/2
1-1/2×11-1/2NPT 1-47/64
2x 11-1/2NPT 2-7/32

BSW

British Standard Whitworth

Tap Size TPI Tapping Drill Diameter
1/16″ 60 1.15
3/32″ 48 1.9
1/8″ 40 2.5
5/32″ 32 3.2
3/16″ 24 3.7
7/32″ 24 4.5
1/4″ 20 5.1
5/16″ 18 6.5
3/8″ 16 7.9
7/16″ 14 9.2
1/2″ 12 10.4
5/8″ 11 13.4
3/4″ 10 16.25
7/8″ 9 19.25
1″ 8 22
1-1/8″ 7 24.5
1-1/4″ 7 27.25
1-3/8″ 6 30.25
1-1/2″ 6 33.5
1-5/8″ 5 35.5
1-3/4″ 5 38.5
1-7/8″ 4 1/2 41.25
2″ 4 1/2 44.5
2-1/4″ 4 50
2-1/2″ 4 56
2-3/4″ 3 1/2 61.5
3″ 3 1/2 68
3-1/4″ 3 1/4 73.75
3-1/2″ 3 1/4 80
3-3/4″ 3 85.5
4″ 3 92
4-1/4″ 2 7/8 98
4-1/2″ 2 7/8 104.2
4-3/4″ 2 3/4 110
5″ 2 3/4 116.5
5-1/4″ 2 5/8 122.5
5-1/2″ 2 5/8 128.5
5-3/4″ 2 1/2 134.5
6″ 2 1/2 141

BSF

British Standard Fine

Tap Size TPI Tapping Drill Diameter
3/16″ 32 4
7/32″ 28 4.6
1/4″ 26 5.3
9/32″ 26 6.1
5/16″ 22 6.8
3/8″ 20 8.3
7/16″ 18 9.7
1/2″ 16 11.1
9/16″ 16 12.7
5/8″ 14 14
11/16″ 14 15.5
3/4″ 12 16.75
13/16″ 12 18.25
7/8″ 11 19.75
1″ 10 22.75
1-1/8″ 9 26.5
1-1/4″ 9 28.75
1-3/8″ 8 31.5
1-1/2″ 8 34.5
1-5/8″ 8 38
1-3/4″ 7 40.5
2″ 7 47
2-1/4″ 6 53
2-1/2″ 6 59
2-3/4″ 6 n/a
3″ 5 n/a
3-1/4″ 5 n/a
3-1/2″ 4 1/2 n/a
3-3/4″ 4 1/2 n/a
4″ 4 1/2 n/a
4-1/4″ 4 n/a

UNEF

Unified National Form

Tap Size TPI Tapping Drill mm
1/4 32 5.6
5/16 32 7.2
3/8 32 8.8
1/2 28 11.8
5/8 24 14.75
3/4 20 18
1 20 24.2

BSB

British Standard Brass

Tap Size TPI Tapping Drill mm
1/4 26 5.2
5/16 26 6.8
3/8 26 8.4
7/16 26 10
1/2 26 11.6
9/16 26 13.2
5/8 26 14.8
3/4 26 18
7/8 26 20.8
1 26 24.3

This information is for a suggested reference only. We accept no responsibility or liability for the above charts. If you find any errors, please contact us. 
Source: Steven L Henderson’s Cutting Edge Designs
Source: WLFuller
Source: Cavalier Cutting Tools Pty Ltd

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