20UN and 20UNR Fixed Pitch Series Thread Chart

Measured in Inches
Size Primary
Inch		 Basic Major Diameter
Inch		 Basic Pitch Diameter
Inch		 Minor Diameter, inch Minor Dia. Area
sq. inch
Tensile Stress Area
sq. inch
External Thread Internal Thread
1/4 0.25 0.2175 0.1905 0.1959 0.0269 0.0318
5/16 0.3125 0.28 0.253 0.2584 0.0481 0.0547
3/8 0.375 0.3425 0.3155 0.3209 0.0755 0.0836
7/16 0.4375 0.405 0.378 0.3834 0.109 0.1187
1/2 0.5 0.4675 0.4405 0.4459 0.1486 0.16
9/16 0.5625 0.53 0.503 0.5084 0.194 0.207
5/8 0.625 0.5925 0.5655 0.5709 0.246 0.261
11/16 0.6875 0.655 0.628 0.6334 0.304 0.32
3/4 0.75 0.7175 0.6905 0.6959 0.369 0.386
13/16 0.8125 0.78 0.753 0.7584 0.439 0.458
7/8 0.875 0.8425 0.8155 0.8209 0.515 0.536
15/16 0.9375 0.905 0.878 0.8834 0.598 0.62
1 1 0.9675 0.9405 0.9459 0.687 0.711
1 - 1/6 1.0625 1.03 1.003 1.0084 0.782 0.807
1 - 1/8 1.125 1.0925 1.0655 1.0709 0.882 0.91
1 - 3/16 1.1875 1.155 1.128 1.1334 0.99 1.018
1 - 1/4 1.25 1.2175 1.1905 1.1959 1.103 1.133
1 - 5/16 1.3125 1.28 1.253 1.2584 1.222 1.254
1 - 3/8 1.375 1.3425 1.3155 1.3209 1.348 1.382
1 - 7/16 1.4375 1.405 1.378 1.3834 1.479 1.51
1 - 1/2 1.5 1.4675 1.4405 1.4459 1.62 1.65
1 - 9/16 1.5625 1.53 1.503 1.5084 1.76 1.8
1 - 5/8 1.625 1.5925 1.5655 1.5709 1.91 1.95
1 - 11/16 1.6875 1.655 1.628 1.6334 2.07 2.11
1 - 3/4 1.75 1.7175 1.6905 1.6959 2.23 2.27
1 - 13/16 1.8125 1.78 1.753 1.7584 2.4 2.44
1 - 7/8 1.875 1.8425 1.8155 1.8209 2.57 2.62
1 - 15/16 1.9375 1.905 1.878 1.8834 2.75 2.8
2 2 1.9675 1.9405 1.9459 2.94 2.99
2 - 1/8 2.125 2.0925 2.0655 2.0709 3.33 3.39
2 - 1/4 2.25 2.2175 2.1905 2.1959 3.75 3.81
2 - 3/8 2.375 2.3425 2.3155 2.3209 4.19 4.25
2 - 1/2 2.5 2.4675 2.4405 2.4459 4.66 4.72
2 - 5/8 2.625 2.5925 2.5655 2.5709 5.15 5.21
2 - 3/4 2.75 2.7175 2.6905 2.6959 5.66 5.73
2 - 7/8 2.875 2.8425 2.8155 2.8209 6.2 6.27
3 3 2.9675 2.9405 2.9459 6.77 6.84