Nominal
Diameter

Major
Diameter
Inch

Major
Diameter
mm

Tapping
Drill Size
mm

TPI

Pitch
mm

#0 - 80 UNF

0.060

1.524

1.25

80

0.317

#1 - 72 UNF

0.073

1.854

1.55

72

0.353

#2 - 64 UNF

0.086

2.184

1.90

64

0.397

#3 - 56 UNF

0.099

2.515

2.15

56

0.453

#4 - 48 UNF

0.112

2.845

2.40

48

0.529

#5 - 44 UNF

0.125

3.175

2.70

44

0.577

#6 - 40 UNF

0.138

3.505

2.95

40

0.635

#8 - 36 UNF

0.164

4.166

3.50

36

0.705

#10 - 32 UNF

0.190

4.826

4.10

32

0.794

#12 - 28 UNF

0.216

5.486

4.70

28

0.907

1/4" - 28 UNF

0.250

6.350

5.50

28

0.907

5/16" - 24 UNF

0.313

7.938

6.90

24

1.058

3/8" - 24 UNF

0.375

9.525

8.50

24

1.058

7/16" - 20 UNF

0.438

11.112

9.90

20

1.270

1/2" - 20 UNF

0.500

12.700

11.50

20

1.270

9/16" - 18 UNF

0.563

14.288

12.90

18

1.411

5/8" - 18 UNF

0.625

15.875

14.50

18

1.411

3/4" - 16 UNF

0.750

19.050

17.50

16

1.587

7/8" - 14 UNF

0.875

22.225

20.40

14

1.814

1" - 12 UNF

1.000

25.400

23.25

12

2.117

1 1/8" - 12 UNF

1.125

28.575

26.50

12

2.117

1 1/4" - 12 UNF

1.250

31.750

29.50

12

2.117

1 3/8" - 12 UNF

1.375

34.925

32.75

12

2.117

1 1/2" - 12 UNF

1.500

38.100

36.00

12

2.117