TAP DRILL SIZES
Recommended drill sizes to use for tapping holes.

 (for approx. 75% thread)


INCH SIZES - 

NC - NATIONAL COARSE

--------------------------------------------------------
TAP		DRILL
SIZE		SIZE
--------------------------------------------------------
#1-64		#53 
#2-56 		#51 
#3-48 		5/64 
#4-40 		#43 
#5-40 		#39 
#6-32 		#36 
#8-32 		#29 
#10-24 		#25 
#12-24 		#17 
1/4-20 		#7 
5/16-18 		F 
3/8-16 		5/16 
7/16-14		U 
1/2-13 		27/64 
9/16-12 		31/64 
5/8-11 		17/32 
3/4-10 		21/32 
7/8-9 		49/64 
1"-8 		7/8 
1-1/8-7 		63/64 
1-1/4-7 		1-7/64 
1-1/2-6 		1-11/32 
1-3/4-5 		1-35/64 
2"-4-1/2 		1-25/32

INCH SIZES - 

NF - NATIONAL FINE

--------------------------------------------------------
TAP		DRILL
SIZE 		SIZE
--------------------------------------------------------
#0-80 		3/64
#1-72 		#53
#2-64 		#50
#3-56 		#46
#4-48 		#42
#5-44 		#37
#6-40 		#33
#8-36 		#29
#10-32 		#21
#12-28 		#15
1/4-28 		#3
5/16-24 		I
3/8-24 		Q
7/16-20 		W
1/2-20 		29/64
9/16-18 		33/64
5/8-18 		37/64
3/4-16 		11/16
7/8-14 		13/16
1"-14 		15/16
1-1/8-12 		1-3/64
1-1/4-12 		1-11/64
1-1/2-12 		1-27/64
1-3/4-12 		1-43/64
2"-12 		1-59/64

 

 

TAPER PIPE SIZES - NPT

--------------------------------------------------------
TAP 		DRILL
SIZE 		SIZE
--------------------------------------------------------
1/8-27 NPT	R
1/4-18 NPT	7/16
3/8-18 NPT	37/64
1/2-14 NPT	23/32
3/4-14 NPT	59/64
1"-11-1/2 NPT	1-5/32
1-1/4-11-1/2 NPT	1-1/2
1-1/2-11-1/2 NPT	1-47/64
2"-11-1/2 NPT	2-7/32
2-1/2-8 NPT	2-5/8
3"-8 NPT		3-1/4
3-1/2-8 NPT	3-3/4
4"-8 NPT		4-1/4

STRAIGHT PIPE SIZES - NPS

--------------------------------------------------------
TAP	 	DRILL
SIZE 		SIZE
--------------------------------------------------------
1/8-27 NPS	S
1/4-18 NPS	29/64
3/8-18 NPS	19/32
1/2-14 NPS	47/64
3/4-14 NPS	15/16
1"-11-1/2 NPS	1-3/16
1-1/4-11-1/2 NPS	1-33/64
1-1/2-11-1/2NPS	1-3/4
2"-11-1/2NPS	2-7/32
2-1/2-8 NPS	2-21/32
3"-8 NPS		3-9/32
3-1/2-8 NPS	3-25/32
4"-8 NPS		4-9/32

Metric