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Fractional Drill Bit

Number Drill Bit

Letter Drill Bit

0-80

3/64

-

-

1-64

-

53

-

2-56

-

50

-

3-48

-

47

-

4-40

3/32

43

-

5-40

-

38

-

6-32

7/64

35

-

8-32

-

29

-

10-24

5/32

25

-

10-32

5/32

21

-

12-24

11/64

16

-

1/4-20

13/64

7

-

1/4-28

7/32

3

-

5/16-18

17/64

-

F

5/16-24

-

-

I

3/8-16

5/16

-

-

3/8-24

21/64

-

Q

7/16-14

23/64

-

U

7/16-20

25/64

-

-

1/2-13

27/64

-

-

1/2-20

29/64

-

-

9/16-12

31/64

-

-

9/16-18

33/64

-

-

5/8-11

17/32

-

-

5/8-18

37/64

-

-

3/4-10

21/32

-

-

3/4-16

11/16

-

-

Drill sizes are for 75% depth of thread.