STI Pitch Diameter Limits For Internal Screw Threads
Classes and Tap Recommendations (USCTI Table 323)
Unified Classes of Thread
Threads Per Inch
Tap Major Diameter
Class 2B For General Applications
Class 3B For Closer Fits
SIze
NC UNC
NF UNF
Minimum Maximum H Limit
Minimum Maximum H Limit
Minimum Maximum
2 3 4 4 6 6 8 8
56 48 40
- - -
0.1107 0.1279 0.1463 0.1409 0.1807 0.1723 0.2067 0.2022 0.2465 0.2327 0.3177 0.2985 0.3874 0.3690 0.4592 0.4315 0.5333 0.5052 0.6032 0.5677 0.6741 0.6374 0.7467 0.6999 0.8835 0.8342 1.0232 0.9708 1.1666 1.1116
0.1117 0.1289 0.1473 0.1419 0.1817 0.1733 0.2077 0.2032 0.2475 0.2337 0.3187 0.2995 0.3884 0.3700 0.4602 0.4325 0.5343 0.5062 0.6042 0.5687 0.6751 0.6384 0.7477 0.7009 0.8850 0.8352 1.0247 0.9718 1.1681 1.1126
H2 H2 H2 H2 H3 H2 H3 H2 H3 H3 H3 H3 H4 H3 H4 H3 H4 H4 H4 H4 H4 H4 H4 H4 H5 H4 H5 H4 H6 H6
0.0981 0.1131 0.1288 0.1261 0.1593 0.1548 0.1853 0.1826 0.2180 0.2113 0.2835 0.2742 0.3501 0.3405 0.4171 0.4030 0.4854 0.4715 0.5514 0.5340 0.6182 0.6001 0.6856 0.6626 0.8169 0.7921 0.9491 0.9234 1.0832 1.0562
0.0986 0.1136 0.1293 0.1266 0.1598 0.1553 0.1858 0.1831 0.2185 0.2118 0.2840 0.2747 0.3506 0.3410 0.4176 0.4035 0.4859 0.4720 0.5519 0.5345 0.6187 0.6006 0.6861 0.6631 0.8174 0.7926 0.9496 0.9239 1.0842 1.0572
H1 H1 H1 H1 H2 H1 H2 H1 H2 H2 H2 H2 H3 H2 H3 H2 H3 H3 H3 H3 H3 H3 H3 H3 H3 H3 H3 H3 H4 H4
0.0976 0.1126 0.1283 0.1256 0.1588 0.1543 0.1848 0.1821 0.2175 0.2108 0.2830 0.2737 0.3496 0.3400 0.4166 0.4025 0.4849 0.4710 0.5509 0.5335 0.6177 0.5996 0.6851 0.6621 0.8159 0.7916 0.9481 0.9224 1.0822 1.0552
0.0981 0.1131 0.1288 0.1261 0.1593 0.1548 0.1853 0.1826 0.2180 0.2113 0.2835 0.2742 0.3501 0.3405 0.4171 0.4030 0.4854 0.4715 0.5514 0.5340 0.6182 0.6001 0.6856 0.6626 0.8164 0.7921 0.9486 0.9229 1.0832 1.0562
-
48
32
-
-
40
32
-
-
36
10 10
24
-
-
32
1/4
20
-
1/4
-
28
5/16 5/16
18
-
-
24
3/8 3/8
16
-
-
24
7/16 7/16
14
-
-
20
1/2 1/2
13
-
-
20
9/16 9/16
12
-
-
18
5/8 5/8 3/4 3/4 7/8 7/8
11
-
-
18
10
-
-
16
9
-
-
14
1 1
8
-
-
12
ISO Metric Class of Threads Class 6H For Commercial Threads
Pitch Diameter Limits
Size (mm)
Recommended Taps
Pitch (mm)
Min.
Max
M2
0.40 0.45 0.50 0.70 0.80 1.00 1.25 1.50 1.75 2.00 2.00 2.50 2.50 2.50 3.00
0.0889 0.1099 0.1309 0.1753 0.2173 0.2618 0.3469 0.4320 0.5172 0.6023 0.6810 0.7725 0.8371 0.9300 1.0216
0.0909 0.1120 0.1332 0.1783 0.2203 0.2654 0.3508 0.4357 0.5224 0.6078 0.6867 0.7786 0.8574 0.9361 1.0289
D2 D2 D2 D3 D3 D3 D3 D4 D4 D5 D5 D5 D5 D5 D6
M2.5
M3 M4 M5 M6 M8
M10 M12 M14 M16 M18 M20 M22 M24
Threading Technical
769
osgtool.com
Powered by FlippingBook