Tap Chart - Pipe Threads
Tap
size		 Threads
per inch		 Drill size w/ taper
pipe reamer		 Drill size w/out
taper pipe reamer		 Straight pipe
threads

1/16

27

15/64

D

1/4

1/8

27

21/64

Q

11/32

1/4

18

27/64

7/16

29/64

3/8

18

9/16

37/64

37/64

1/2

14

11/16

23/32

23/32

3/4

14

57/64

59/64

15/16

1

11.5

1 1/8

1 5/32

1 11/64

1 1/4

11.5

1 15/32

1 1/2

1 33/64

1 1/2

11.5

1 23/32

1 47/64

1 3/4

2

11.5

2 3/16

2 7/32

2 7/32