CLASSES : 2B & 3B

Tap Recommendations for Classes 2B and 3B

Unified Inch Screw Threads

Tap Size/Pitch	Recommended Tap Limits				Basic Major Diameter	Basic Pitch Diameter	Maximum PD-2B	Maximum PD-3B
	Class 2B		Class 3B
	Cut Tap	Form Tap	Cut Tap	Form Tap
0-80	H2	H3	H1	H2	.0600	.0519	.0542	.0536
1-64	H2	H3	H1	H2	.0730	.0629	.0655	.0648
1-72	H2	H3	H1	H2	.0730	.0640	.0665	.0659
2-56	H2	H3	H1	H2	.0860	.0744	.0772	.0765
2-64	H2	H3	H1	H2	.0860	.0759	.0786	.0779
3-48	H2	H3	H1	H2	.0990	.0855	.0885	.0877
3-56	H2	H3	H1	H2	.0990	.0874	.0902	.0895
4-40	H2	H5	H2	H3	.1120	.0958	.0991	.0982
4-48	H2	H5	H1	H3	.1120	.0985	.1016	.1008
5-40	H2	H5	H2	H3	.1250	.1088	.1121	.1113
5-44	H2	H5	H1	H3	.1250	.1102	.1134	.1126
6-32	H3	H5	H2	H3	.1380	.1177	.1214	.1204
6-40	H2	H5	H2	H3	.1380	.1218	.1252	.1243
8-32	H3	H5	H2	H3	.1640	.1437	.1475	.1465
8-36	H2	H5	H2	H3	.1640	.1460	.1496	.1487
10-24	H3	H6	H3	H4	.1900	.1629	.1672	.1661
10-32	H3	H6	H2	H4	.1900	.1697	.1736	.1726
12-24	H3	H6	H3	H4	.2160	.1889	.1933	.1922
12-28	H3	H6	H3	H4	.2160	.1928	.1970	.1959
1/4-20	H5	H6	H3	H4	.2500	.2175	.2223	.2211
1/4-28	H4	H6	H3	H4	.2500	.2268	.2311	.2300
5/16-18	H5	H7	H3	H5	.3125	.2764	.2817	.2803
5/16-24	H4	H7	H3	H5	.3125	.2854	.2902	.2890
3/8-16	H5	H7	H3	H5	.3750	.3344	.3401	.3387
3/8-24	H4	H7	H3	H5	.3750	.3479	.3528	.3516
7/16-14	H5	H8	H3	H5	.4375	.3911	.3972	.3957
7/16-20	H5	H8	H3	H5	.4375	.4050	.4104	.4091
1/2-13	H5	H8	H3	H6	.5000	.4500	.4565	.4548
1/2-20	H5	H8	H3	H5	.5000	.4675	.4731	.4717
9/16-12	H5	H10	H3	H7	.5625	.5084	.5152	.5135
9/16-18	H5	H10	H3	H7	.5625	.5264	.5323	.5308
5/8-11	H5	H10	H3	H7	.6250	.5660	.5732	.5714
5/8-18	H5	H10	H3	H7	.6250	.5889	.5949	.5934
3/4-10	H5	H10	H5	H7	.7500	.6850	.6927	.6907
3/4-16	H5	H10	H3	H7	.7500	.7094	.7159	.7143
7/8-9	H6	H12	H4	H8	.8750	.8028	.8110	.8089
7/8-14	H6	H12	H4	H8	.8750	.8286	.8356	.8339
1-8	H6	H12	H4	H8	1.0000	.9188	.9276	.9254
1-12	H6	H12	H4	H8	1.0000	.9459	.9535	.9516
1 1/8-7	H8	H12	H4	H8	1.1250	1.0332	1.0416	1.0393
1 1/8-12	H6	H12	H4	H8	1.1250	1.0709	1.0787	1.0768
1 1/4-7	H8	H12	H4	H8	1.2500	1.1572	1.1668	1.1644
1 1/4-12	H6	H12	H4	H8	1.2500	1.1959	1.2039	1.2019
1 3/8-6	H8	H14	H4	H8	1.3750	1.2667	1.2771	1.2745
1 3/8-12	H6	H14	H4	H8	1.3750	1.3209	1.3291	1.3270
1 1/2-6	H8	H14	H4	H8	1.5000	1.3917	1.4022	1.3996
1 1/2-12	H6	H14	H4	H8	1.5000	1.4459	1.4542	1.4522

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