American Standard Screw Gauges
The sizes in the first column that are not followed by an inch mark are
American Standard Screw gauges. Shading indicates sizes no longer in use or
whose use is discouraged by standards organizations. See this
table for diameters of tap drills.
The NS series is a catch-all category for threads which have the American
Standard form, but whose pitches are not in the National Coarse or National Fine
series.
The tap drill sizes are listed in the order in which the tpi are listed in
the previous column.
|
Gage and
Fractional
Sizes |
Major diam.
(inches) |
Clearance
Drill |
NC & UNC
tpi |
Tap Drill
for UNC |
NF & UNF
tpi |
Tap Drill
for UNF |
NEF |
NS |
Tap drill
for NS |
Nut Size |
|
0000 |
|
#73 |
160 |
1⁄64″ |
|
|
|
|
|
|
|
000 |
|
#63 |
120 |
#71 |
|
|
|
|
|
3⁄32″ |
|
00 |
|
#55 |
90 |
#65 |
|
|
|
|
|
3⁄32″ |
|
0 |
0.060 |
#52 |
— |
— |
80 |
3⁄64″ |
|
|
|
5⁄32″ |
|
1 |
0.073 |
#48 |
64 |
#52 |
72 |
#53 |
|
56 |
#54 |
5⁄32″ |
|
2 |
0.086 |
#43 |
56 |
#50 |
64 |
#50 |
|
— |
— |
3⁄16″ |
|
3 |
0.099 |
#38 |
48 |
#47 |
56 |
#45 |
|
— |
— |
3⁄16″ |
|
4 |
0.112 |
#33 |
40 |
#43 |
48 |
#42 |
|
32,36 |
45,44 |
¼″ |
|
5 |
0.125 |
#30 |
40 |
#39 |
44 |
#37 |
|
36 |
40 |
¼″ |
|
6 |
0.138 |
#28 |
32 |
#36 |
40 |
#33 |
|
36 |
34 |
5⁄16″ |
|
7 |
0.151 |
|
— |
— |
— |
— |
|
30,32,36 |
31,31,
1⁄8″ |
5⁄16″ |
|
8 |
0.164 |
#19 |
32 |
#29 |
36 |
#29 |
|
30,
40 |
30,28 |
11⁄32″ |
|
9 |
0.177 |
|
— |
— |
— |
— |
|
24,30,32 |
29,27,
26 |
11⁄32″ |
|
10 |
0.190 |
#11 |
24 |
#25 |
32 |
#21 |
|
28,30 |
23,22 |
3⁄8″ |
|
12 |
0.216 |
|
24 |
|
28 |
|
|
32 |
13 |
7⁄16″ |
|
14 |
0.242 |
D |
|
|
|
|
|
20,24 |
10,7 |
7⁄16″ |
|
¼″ |
0.250 |
¼″ or E |
20 |
#7 |
28 |
#3 |
32 |
24,27,32 |
4,3,7⁄32″ |
7⁄16″ |
|
16 |
0.268 |
|
— |
— |
— |
— |
|
18, 20, 22 |
7⁄32″,2 |
½″ |
|
18 |
0.294 |
|
— |
— |
— |
— |
|
18, 20 |
B,D |
9⁄16″ |
|
5⁄16″ |
0.3125 |
O |
18 |
F |
24 |
I |
32 |
20, 27, 32 |
17⁄64″,
J,
9⁄32 |
9⁄16″ |
|
20 |
0.320 |
|
|
|
|
|
|
16, 18, 20 |
G,17⁄64″,I |
5⁄8″ |
|
22 |
0.346 |
|
|
|
|
|
|
16, 18 |
9⁄32″,L |
5⁄8″ |
|
24 |
0.372 |
|
|
|
|
|
|
16, 18 |
5⁄16″,O |
5⁄8″ |
|
3⁄8″ |
0.375 |
V |
16 |
5⁄16″ |
24 |
Q |
32 |
20, 27 |
|
5⁄8″ |
|
26 |
0.398 |
Y |
|
|
|
|
|
14, 16 |
21⁄64″,R |
11⁄16″ |
|
28 |
0.424 |
7⁄16″ |
|
|
|
|
|
14, 16 |
T,23⁄64″ |
11⁄16″ |
|
7⁄16″ |
0.4375 |
7⁄16″ |
14 |
U |
20 |
25⁄64″ |
28 |
24, 27 |
|
|
|
30 |
0.450 |
29⁄64″ |
|
|
|
|
|
14, 16 |
V,25⁄64″ |
7⁄8″ |
|
½″ |
0.5000 |
½″ |
13 (see note 1) |
27⁄64″ |
20 |
29⁄64″ |
28 |
12, 24, 27 |
|
|
|
12 |
|
|
|
|
|
|
¾″ |
|
9⁄16″ |
0.5625 |
9⁄16″ |
12 |
31⁄64″ |
18 |
33⁄64″ |
24 |
27 |
|
|
|
5⁄8″ |
0.6250 |
5⁄8″ |
11 |
17⁄32″ |
18 |
37⁄64″ |
24 |
12,
27 |
|
|
|
11⁄16″ |
0.68753 |
11⁄16 |
|
|
|
|
24 |
|
|
|
|
¾″ |
0.7500 |
|
10 |
21⁄32″ |
16 |
|
20 |
12,
27 |
|
11⁄8″ |
|
7⁄8″ |
0.8750 |
|
9 |
49⁄64″ |
14 |
|
20 |
12,
18,
27 |
|
15⁄16″ |
|
1″ |
1.0000 |
|
8 |
7⁄8″ |
14 |
|
20 |
12,
27 |
|
1½″ |
|
