Internal Screw Threads Dimension Chart

ANSI standards keep those values consistent, so a concise thread dimensions chart helps you verify common internal thread sizes at a glance. We’ve highlighted quick checks like 8-32 minor diameter, 6-32 major diameter, 4-40 minor diameter, and 1/4-20 minor diameter so you don’t have to dig through multiple tables. Use this reference to confirm fit for internal threads during design, inspection, or when selecting tap drills.

ANSI Internal Thread Sizes

Screw Size	Thread Class	Major Diameter Min	Major Diameter Basic	Major Diameter Max	Pitch Diameter Min	Pitch Diameter Max	Minor Diameter Max
0-80	2B	0.0600	0.0600	0.0620	0.0519	0.0534	0.0465
0-80	3B	0.0600	0.0600	0.0614	0.0519	0.0529	0.0462
1-64	2B	0.0730	0.0730	0.0760	0.0640	0.0657	0.0580
1-64	3B	0.0730	0.0730	0.0752	0.0640	0.0651	0.0576
1-72	2B	0.0730	0.0730	0.0760	0.0650	0.0667	0.0590
1-72	3B	0.0730	0.0730	0.0752	0.0650	0.0661	0.0586
2-56	2B	0.0860	0.0860	0.0890	0.0768	0.0785	0.0705
2-56	3B	0.0860	0.0860	0.0882	0.0768	0.0779	0.0701
2-64	2B	0.0860	0.0860	0.0890	0.0778	0.0795	0.0715
2-64	3B	0.0860	0.0860	0.0882	0.0778	0.0789	0.0711
3-48	2B	0.0990	0.0990	0.1020	0.0896	0.0913	0.0828
3-48	3B	0.0990	0.0990	0.1012	0.0896	0.0907	0.0824
3-56	2B	0.0990	0.0990	0.1020	0.0906	0.0923	0.0838
3-56	3B	0.0990	0.0990	0.1012	0.0906	0.0917	0.0834
4-40	2B	0.1120	0.1120	0.1150	0.1013	0.1030	0.0938
4-40	3B	0.1120	0.1120	0.1142	0.1013	0.1024	0.0934
4-48	2B	0.1120	0.1120	0.1150	0.1028	0.1045	0.0953
4-48	3B	0.1120	0.1120	0.1142	0.1028	0.1039	0.0949
5-40	2B	0.1250	0.1250	0.1280	0.1138	0.1155	0.1063
5-40	3B	0.1250	0.1250	0.1272	0.1138	0.1149	0.1059
5-44	2B	0.1250	0.1250	0.1280	0.1148	0.1165	0.1073
5-44	3B	0.1250	0.1250	0.1272	0.1148	0.1159	0.1069
6-32	2B	0.1380	0.1380	0.1420	0.1234	0.1256	0.1109
6-32	3B	0.1380	0.1380	0.1409	0.1234	0.1250	0.1104
6-40	2B	0.1380	0.1380	0.1420	0.1257	0.1279	0.1149
6-40	3B	0.1380	0.1380	0.1409	0.1257	0.1273	0.1144
8-32	2B	0.1640	0.1640	0.1680	0.1494	0.1516	0.1369
8-32	3B	0.1640	0.1640	0.1669	0.1494	0.1510	0.1364
8-36	2B	0.1640	0.1640	0.1680	0.1512	0.1534	0.1389
8-36	3B	0.1640	0.1640	0.1669	0.1512	0.1528	0.1384
10-24	2B	0.1900	0.1900	0.1950	0.1696	0.1722	0.1560
10-24	3B	0.1900	0.1900	0.1935	0.1696	0.1716	0.1554
10-32	2B	0.1900	0.1900	0.1950	0.1762	0.1788	0.1626
10-32	3B	0.1900	0.1900	0.1935	0.1762	0.1782	0.1620
1/4-20	2B	0.2500	0.2500	0.2560	0.2278	0.2309	0.2113
1/4-20	3B	0.2500	0.2500	0.2540	0.2278	0.2303	0.2105
1/4-28	2B	0.2500	0.2500	0.2560	0.2354	0.2385	0.2218
1/4-28	3B	0.2500	0.2500	0.2540	0.2354	0.2379	0.2210
5/16-18	2B	0.3125	0.3125	0.3190	0.2850	0.2884	0.2674
5/16-18	3B	0.3125	0.3125	0.3169	0.2850	0.2878	0.2665
5/16-24	2B	0.3125	0.3125	0.3190	0.2929	0.2963	0.2768
5/16-24	3B	0.3125	0.3125	0.3169	0.2929	0.2957	0.2759
3/8-16	2B	0.3750	0.3750	0.3820	0.3423	0.3460	0.3239
3/8-16	3B	0.3750	0.3750	0.3797	0.3423	0.3454	0.3229
3/8-24	2B	0.3750	0.3750	0.3820	0.3507	0.3544	0.3344
3/8-24	3B	0.3750	0.3750	0.3797	0.3507	0.3538	0.3334
7/16-14	2B	0.4375	0.4375	0.4455	0.3991	0.4032	0.3794
7/16-14	3B	0.4375	0.4375	0.4429	0.3991	0.4026	0.3782
7/16-20	2B	0.4375	0.4375	0.4455	0.4137	0.4178	0.3962
7/16-20	3B	0.4375	0.4375	0.4429	0.4137	0.4172	0.3950
1/2-13	2B	0.5000	0.5000	0.5090	0.4565	0.4610	0.4358
1/2-13	3B	0.5000	0.5000	0.5061	0.4565	0.4603	0.4345
1/2-20	2B	0.5000	0.5000	0.5090	0.4762	0.4807	0.4591
1/2-20	3B	0.5000	0.5000	0.5061	0.4762	0.4800	0.4578
9/16-12	2B	0.5625	0.5625	0.5720	0.5138	0.5187	0.4920
9/16-12	3B	0.5625	0.5625	0.5689	0.5138	0.5180	0.4905
9/16-18	2B	0.5625	0.5625	0.5720	0.5302	0.5351	0.5129
9/16-18	3B	0.5625	0.5625	0.5689	0.5302	0.5344	0.5114
5/8-11	2B	0.6250	0.6250	0.6355	0.5723	0.5777	0.5493
5/8-11	3B	0.6250	0.6250	0.6321	0.5723	0.5769	0.5476
5/8-18	2B	0.6250	0.6250	0.6355	0.5929	0.5983	0.5766
5/8-18	3B	0.6250	0.6250	0.6321	0.5929	0.5975	0.5751
3/4-10	2B	0.7500	0.7500	0.7620	0.6891	0.6952	0.6639
3/4-10	3B	0.7500	0.7500	0.7581	0.6891	0.6943	0.6619
3/4-16	2B	0.7500	0.7500	0.7620	0.7213	0.7274	0.7029
3/4-16	3B	0.7500	0.7500	0.7581	0.7213	0.7265	0.7009
7/8-9	2B	0.8750	0.8750	0.8885	0.8065	0.8133	0.7794
7/8-9	3B	0.8750	0.8750	0.8843	0.8065	0.8123	0.7771
7/8-14	3B	0.8750	0.8750	0.8843	0.8428	0.8489	0.8196
1-8	2B	1.0000	1.0000	1.0150	0.9196	0.9272	0.8903
1-8	3B	1.0000	1.0000	1.0105	0.9196	0.9261	0.8877
1-12	2B	1.0000	1.0000	1.0150	0.9567	0.9643	0.9349
1-12	3B	1.0000	1.0000	1.0105	0.9567	0.9632	0.9323
1-1/8-7	2B	1.1250	1.1250	1.1420	1.0563	1.0649	1.0235
1-1/8-12	2B	1.1250	1.1250	1.1420	1.0817	1.0903	1.0599
1-3/8-6	2B	1.3750	1.3750	1.3950	1.3053	1.3156	1.2667
1-3/8-12	2B	1.3750	1.3750	1.3950	1.3317	1.3420	1.3099
1-1/2-6	2B	1.5000	1.5000	1.5200	1.4303	1.4406	1.3917
1-1/2-12	2B	1.5000	1.5000	1.5200	1.4567	1.4670	1.4349
1-3/4-5	2B	1.7500	1.7500	1.7750	1.6751	1.6875	1.6313
2-6	2B	2.0000	2.0000	2.0300	1.9303	1.9436	1.8917

Conclusion

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The content on this webpage is for informational purposes only. MISUMI makes no guarantees, expressed or implied, regarding the accuracy, completeness, or validity of the information. Performance parameters, tolerances, designs, materials, or processes should not be assumed to reflect third-party suppliers’ or manufacturers’ deliverables within MISUMI’s network. Buyers are responsible for specifying their part requirements.

Internal Screw Threads Size Chart

Conclusion

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