Recommended tap drill sizes (for appx. 75% thread) — INCH and
METRIC
INCH SIZES - NATIONAL COARSE
TAP SIZE
DRILL 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
TAP SIZE
DRILL 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
TAPER PIPE SIZES - NPT
TAP SIZE
DRILLSIZE
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
TAP SIZE
Drill 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
METRIC COARSE SIZES
TAP SIZE
DRILL 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
METRIC FINE SIZES
TAP SIZE
DRILL 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
____________________________________________________________________________ Note: The CHRA does not warrant that the information
provided is true or correct. It is up to the own individual to do their
own checks (with A.C.T Rego or a qualified Engineer) and the A.C.T
Technical Advisory Committee (ACT TAC). Email the ACT TAC for advice BEFORE you
start! ____________________________________________________________________________
Tap &
Drill Sizes 