Nominal
Diameter

Major
Diameter
Inch

Major
Diameter
mm

Tapping
Drill Size
mm

TPI

Pitch
mm

#1 - 64 UNC

0.073

1.854

1.50

64

0.397

#2 - 56 UNC

0.086

2.184

1.78

56

0.453

#3 - 48 UNC

0.099

2.515

2.05

48

0.529

#4 - 40 UNC

0.112

2.845

2.27

40

0.635

#5 - 40 UNC

0.125

3.175

2.59

40

0.635

#6 - 32 UNC

0.138

3.505

2.77

32

0.794

#8 - 32 UNC

0.164

4.166

3.42

32

0.794

#10 - 24 UNC

0.190

4.826

3.82

24

1.058

#12 - 24 UNC

0.216

5.486

4.47

24

1.058

1/4" - 20 UNC

0.250

6.350

5.11

20

1.270

5/16" - 18 UNC

0.313

7.938

6.55

18

1.411

3/8" - 16 UNC

0.375

9.525

7.95

16

1.587

7/16" - 14 UNC

0.438

11.112

9.30

14

1.814

1/2" - 13 UNC

0.500

12.700

10.73

13

1.954

9/16" - 12 UNC

0.563

14.288

12.15

12

2.117

5/8" - 11 UNC

0.625

15.875

13.53

11

2.309

3/4" - 10 UNC

0.750

19.050

16.46

10

2.540

7/8" - 9 UNC

0.875

22.225

19.34

9

2.822

1" - 8 UNC

1.000

25.400

22.15

8

3.175

1 1/8" - 7 UNC

1.125

28.575

24.87

7

3.628

1 1/4" - 7 UNC

1.250

31.750

28.85

7

3.628

1 3/8" - 6 UNC

1.375

34.925

30.60

6

4.233

1 1/2" - 6 UNC

1.500

38.100

33.70

6

4.233

1 3/4" - 5 UNC

1.750

44.450

39.26

5

5.080

2" - 4 1/2 UNC

2.000

50.800

45.03

4.5

5.644

2 1/4" - 4 1/2 UNC

2.250

57.150

51.38

4.5

5.644

2 1/2" - 4 UNC

2.500

63.500

57.00

4

6.350

2 3/4" - 4 UNC

2.750

69.850

63.36

4

6.350

3" - 4 UNC

3.000

76.200

69.71

4

6.350

3 1/4" - 4 UNC

3.250

82.550

76.06

4

6.350

3 1/2" - 4 UNC

3.500

88.900

82.41

4

6.350

3 3/4" - 4 UNC

3.750

95.250

88.76

4

6.350

4" - 4 UNC

4.000

101.600

95.11

4

6.350