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°.

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