American National Thread
ANSI/ACME B1.5-1977

The ACME thread was developed as a compromise, to offer better strength than a V-form while overcoming the problems with the square thread form.
The flank angle is 29°.

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Nominal Diameter	Major Diameter Inch	Major Diameter mm	Tapping Drill Size mm	TPI	Pitch mm
1/4" - 16 ACME	0.250	6.350	4.762	16	1.588
5/16" - 14 ACME	0.313	7.938	6.123	14	1.814
3/8" - 12 ACME	0.375	9.525	7.408	12	2.117
7/16" - 12 ACME	0.437	11.112	8.996	12	2.117
1/2" - 10 ACME	0.500	12.700	10.160	10	2.540
5/8" - 8 ACME	0.625	15.875	12.700	8	3.175
3/4" - 6 ACME	0.750	19.050	14.817	6	4.233
7/8" - 6 ACME	0.875	22.225	17.992	6	4.233
1" - 5 ACME	1.000	25.400	20.320	5	5.080
1 1/8" - 5 ACME	1.125	28.575	23.495	5	5.080
1 1/4" - 5 ACME	1.250	31.750	26.670	5	5.080
1 3/8" - 4 ACME	1.375	34.925	28.575	4	6.350
1 1/2" - 4 ACME	1.500	38.100	31.750	4	6.350
1 3/4" - 4 ACME	1.750	44.450	38.100	4	6.350
2" - 4 ACME	2.000	50.800	44.450	4	6.350
2 1/4" - 3 ACME	2.250	57.150	48.683	3	8.467
2 1/2" - 3 ACME	2.500	63.500	55.033	3	8.467
2 3/4" - 3 ACME	2.750	69.850	61.383	3	8.467
3" - 2 ACME	3.000	76.200	63.500	2	12.700
3 1/2" - 2 ACME	3.500	88.900	76.200	2	12.700
4" - 2 ACME	4.000	101.600	88.900	2	12.700
4 1/2" - 2 ACME	4.500	114.300	101.600	2	12.700
5" - 2 ACME	5.000	127.000	114.300	2	12.700
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