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Drill and Tap Charts - Inch &
Metric
INCH TAP DRILL SIZES
Recommended tap drill sizes (for approx. 75% thread)
INCH SIZES - 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
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INCH SIZES - 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
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TAPER PIPE SIZES - NPT----------------------------
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
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STRAIGHT PIPE SIZES - NPS----------------------------
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----------------------------
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----------------------------
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 7.5
8 x .75 7.25
8 x 1 7
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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Handy Helpers!
Tap Drill Sizes (inch) for a
75% Thread
In general, you can find the tap-drill for any size 60 degree thread, subtract
one pitch length from the major diameter.
Formula:
Major Dia. minus One Pitch Length equals
tap-drill size
English Example for 3/8-16
thread: .375 - .0625 = .3125 tap-drill (5/16)
Metric Example for M6 X 1
thread: 6mm - 1mm = 5mm tap-drill
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