Last updated 10 August 2026
Yes, below, and it is computed rather than transcribed: seventeen sizes across four classes, from the basic geometry and the ASME B1.1 tolerance formula.
Every other thread table on the internet is a transcription, which means it can be wrong in one row and nobody can tell by looking. This one is derived, the method is published beside it, and eleven of its rows are pinned against printed tables in the engine's own tests. You can check the arithmetic rather than having to trust the typist.
Classes 1A and 1B are not here. Their tolerance relationship is widely repeated and we could not verify it against a printed table, so they are absent rather than approximated. Major and minor diameter limits are absent for the same reason: a different set of formulas this engine does not carry.
| Size | Class | Basic PD | Allowance | Tolerance | PD max | PD min |
|---|---|---|---|---|---|---|
| #4-40 UNC | 2A | 0.0958 | 0.0008 | 0.0025 | 0.095 | 0.0925 |
| #4-40 UNC | 3A | 0.0958 | none | 0.0019 | 0.0958 | 0.0939 |
| #4-40 UNC | 2B | 0.0958 | none | 0.0033 | 0.0991 | 0.0958 |
| #4-40 UNC | 3B | 0.0958 | none | 0.0024 | 0.0982 | 0.0958 |
| #6-32 UNC | 2A | 0.1177 | 0.0008 | 0.0028 | 0.1169 | 0.1141 |
| #6-32 UNC | 3A | 0.1177 | none | 0.0021 | 0.1177 | 0.1156 |
| #6-32 UNC | 2B | 0.1177 | none | 0.0037 | 0.1214 | 0.1177 |
| #6-32 UNC | 3B | 0.1177 | none | 0.0028 | 0.1205 | 0.1177 |
| #8-32 UNC | 2A | 0.1437 | 0.0009 | 0.0029 | 0.1428 | 0.1399 |
| #8-32 UNC | 3A | 0.1437 | none | 0.0022 | 0.1437 | 0.1415 |
| #8-32 UNC | 2B | 0.1437 | none | 0.0038 | 0.1475 | 0.1437 |
| #8-32 UNC | 3B | 0.1437 | none | 0.0028 | 0.1465 | 0.1437 |
| #10-24 UNC | 2A | 0.1629 | 0.001 | 0.0033 | 0.1619 | 0.1586 |
| #10-24 UNC | 3A | 0.1629 | none | 0.0025 | 0.1629 | 0.1604 |
| #10-24 UNC | 2B | 0.1629 | none | 0.0043 | 0.1672 | 0.1629 |
| #10-24 UNC | 3B | 0.1629 | none | 0.0032 | 0.1661 | 0.1629 |
| #10-32 UNF | 2A | 0.1697 | 0.0009 | 0.003 | 0.1688 | 0.1658 |
| #10-32 UNF | 3A | 0.1697 | none | 0.0023 | 0.1697 | 0.1674 |
| #10-32 UNF | 2B | 0.1697 | none | 0.0039 | 0.1736 | 0.1697 |
| #10-32 UNF | 3B | 0.1697 | none | 0.0029 | 0.1726 | 0.1697 |
| 1/4-20 UNC | 2A | 0.2175 | 0.0011 | 0.0037 | 0.2164 | 0.2127 |
| 1/4-20 UNC | 3A | 0.2175 | none | 0.0028 | 0.2175 | 0.2147 |
| 1/4-20 UNC | 2B | 0.2175 | none | 0.0048 | 0.2223 | 0.2175 |
| 1/4-20 UNC | 3B | 0.2175 | none | 0.0036 | 0.2211 | 0.2175 |
| 1/4-28 UNF | 2A | 0.2268 | 0.001 | 0.0033 | 0.2258 | 0.2225 |
| 1/4-28 UNF | 3A | 0.2268 | none | 0.0025 | 0.2268 | 0.2243 |
| 1/4-28 UNF | 2B | 0.2268 | none | 0.0043 | 0.2311 | 0.2268 |
| 1/4-28 UNF | 3B | 0.2268 | none | 0.0032 | 0.23 | 0.2268 |
| 5/16-18 UNC | 2A | 0.2764 | 0.0012 | 0.004 | 0.2752 | 0.2712 |
| 5/16-18 UNC | 3A | 0.2764 | none | 0.003 | 0.2764 | 0.2734 |
| 5/16-18 UNC | 2B | 0.2764 | none | 0.0053 | 0.2817 | 0.2764 |
| 5/16-18 UNC | 3B | 0.2764 | none | 0.0039 | 0.2803 | 0.2764 |
| 5/16-24 UNF | 2A | 0.2854 | 0.0011 | 0.0037 | 0.2843 | 0.2806 |
| 5/16-24 UNF | 3A | 0.2854 | none | 0.0027 | 0.2854 | 0.2827 |
| 5/16-24 UNF | 2B | 0.2854 | none | 0.0048 | 0.2902 | 0.2854 |
| 5/16-24 UNF | 3B | 0.2854 | none | 0.0036 | 0.289 | 0.2854 |
| 3/8-16 UNC | 2A | 0.3344 | 0.0013 | 0.0044 | 0.3331 | 0.3287 |
| 3/8-16 UNC | 3A | 0.3344 | none | 0.0033 | 0.3344 | 0.3311 |
| 3/8-16 UNC | 2B | 0.3344 | none | 0.0057 | 0.3401 | 0.3344 |
| 3/8-16 UNC | 3B | 0.3344 | none | 0.0043 | 0.3387 | 0.3344 |
| 3/8-24 UNF | 2A | 0.3479 | 0.0011 | 0.0038 | 0.3468 | 0.343 |
| 3/8-24 UNF | 3A | 0.3479 | none | 0.0029 | 0.3479 | 0.345 |
| 3/8-24 UNF | 2B | 0.3479 | none | 0.0049 | 0.3528 | 0.3479 |
| 3/8-24 UNF | 3B | 0.3479 | none | 0.0037 | 0.3516 | 0.3479 |
| 7/16-14 UNC | 2A | 0.3911 | 0.0014 | 0.0047 | 0.3897 | 0.385 |
| 7/16-14 UNC | 3A | 0.3911 | none | 0.0035 | 0.3911 | 0.3876 |
| 7/16-14 UNC | 2B | 0.3911 | none | 0.0061 | 0.3972 | 0.3911 |
| 7/16-14 UNC | 3B | 0.3911 | none | 0.0046 | 0.3957 | 0.3911 |
| 1/2-13 UNC | 2A | 0.45 | 0.0015 | 0.005 | 0.4485 | 0.4435 |
| 1/2-13 UNC | 3A | 0.45 | none | 0.0037 | 0.45 | 0.4463 |
| 1/2-13 UNC | 2B | 0.45 | none | 0.0065 | 0.4565 | 0.45 |
| 1/2-13 UNC | 3B | 0.45 | none | 0.0048 | 0.4548 | 0.45 |
| 1/2-20 UNF | 2A | 0.4675 | 0.0013 | 0.0043 | 0.4662 | 0.4619 |
| 1/2-20 UNF | 3A | 0.4675 | none | 0.0032 | 0.4675 | 0.4643 |
| 1/2-20 UNF | 2B | 0.4675 | none | 0.0056 | 0.4731 | 0.4675 |
| 1/2-20 UNF | 3B | 0.4675 | none | 0.0042 | 0.4717 | 0.4675 |
| 5/8-11 UNC | 2A | 0.566 | 0.0017 | 0.0055 | 0.5643 | 0.5588 |
| 5/8-11 UNC | 3A | 0.566 | none | 0.0041 | 0.566 | 0.5619 |
| 5/8-11 UNC | 2B | 0.566 | none | 0.0072 | 0.5732 | 0.566 |
| 5/8-11 UNC | 3B | 0.566 | none | 0.0054 | 0.5714 | 0.566 |
| 3/4-10 UNC | 2A | 0.685 | 0.0018 | 0.0059 | 0.6832 | 0.6773 |
| 3/4-10 UNC | 3A | 0.685 | none | 0.0044 | 0.685 | 0.6806 |
| 3/4-10 UNC | 2B | 0.685 | none | 0.0077 | 0.6927 | 0.685 |
| 3/4-10 UNC | 3B | 0.685 | none | 0.0057 | 0.6907 | 0.685 |
| 1-8 UNC | 2A | 0.9188 | 0.002 | 0.0068 | 0.9168 | 0.91 |
| 1-8 UNC | 3A | 0.9188 | none | 0.0051 | 0.9188 | 0.9137 |
| 1-8 UNC | 2B | 0.9188 | none | 0.0088 | 0.9276 | 0.9188 |
| 1-8 UNC | 3B | 0.9188 | none | 0.0066 | 0.9254 | 0.9188 |
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Unified inch screw thread pitch diameter limits. ASME B1.1, Federal Screw Thread Specification H28. CC-BY-4.0, attribute to ctrlPlanner.
This is one characteristic. A real part has forty of them through five operations, and every one needs the same walk when the drawing revises. That is what ctrlPlanner does from a ballooned print.
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