Tap Drill Sizes

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INCH TAP DRILL SIZES
Recommended tap drill sizes (for approx. 75% thread)


INCH SIZES - NATIONAL COARSE

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TAP		DRILL
SIZE		SIZE
----------------------------
#0-80 		3/64" 
#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 - NATIONAL FINE

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TAP		DRILL
SIZE 		SIZE
----------------------------
#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

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TAPER PIPE SIZES - NPT

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

STRAIGHT PIPE SIZES - NPS

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


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METRIC TAP DRILL SIZES
Recommended tap drill sizes (for approx. 75% thread)

METRIC COARSE SIZES

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TAP                 DRILL
SIZE                SIZE
----------------------------
1mm x .25            .75mm
1.1 x .25            .85
1.2 x .25            .95
1.4 x .3            1.1
1.6 x .35           1.25
1.7 x .35           1.3
1.8 x .35           1.45
2 x .4              1.6
2.2 x .45           1.75
2.5 x .45           2.05
3 x .5              2.5
3.5 x .6            2.9
4 x .7              3.3
4.5 x .75           3.7
5 x .8              4.2
6 x 1               5
7 x 1               6
8 x 1.25            6.8
9 x 1.25            7.8
10 x 1.5            8.5
11 x 1.5            9.5
12 x 1.75           10.2
14 x 2              12
16 x 2              14
18 x 2.5            15.5
20 x 2.5            17.5
22 x 2.5            19.5
24 x 3              21
27 x 3              24
30 x 3.5            26.5
33 x 3.5            29.5
36 x 4              32
39 x 4              35








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METRIC FINE SIZES

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TAP                 DRILL
SIZE                SIZE
----------------------------
4 mm x .35          3.6mm
4 x .5              3.5
5 x .5              4.5
6 x .5              5.5
6 x .75             5.25
7 x .75             6.25
8 x .5              7
8 x .75             7.25
8 x 1               7.5
9 x 1               8
10 x .75            9.25
10 x 1              9
10 x 1.25           8.8 
11 x 1              10
12 x .75            11.25
12 x 1              11
12 x 1.5            10.5
14 x 1              13
14 x 1.25           12.8
14 x 1.5            12.5
16 x 1              15
16 x 1.5            14.5
18 x 1              17
18 x 2              16
20 x 1              19
20 x 1.5            18.5
20 x 2              18
22 x 1              21
22 x 1.5            20.5
22 x 2              20
24 x 1.5            22.5
24 x 2              22
26 x 1.5            24.5
27 x 1.5            25.5
27 x 2              25 
28 x 1.5            26.5
30 x 1.5            28.5
30 x 2              28
33 x 2              31
36 x 3              33
39 x 3              36
----------------------------

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