Table 4.2 Diameter and net area [a] of Unified Screw Threads UNC and UNF. Coarse Series, UNC Outside Diameter, Fine Series, UNF Threads Net Area, Threads per Net Area, in per Inch, N An, in Inch, N An, in 0.2500 20 0.0318 28 0.0364 0.3125 18 0.0524 24 0.0580 0.3750 16 0.0775 24 0.0878 0.4375 14 0.106 20 0.119 0.5000 13 0.142 20 0.160 0.5625 12 0.182 18 0.203 0.6250 11 0.226 18 0.256 0.7500 10 0.334 16 0.373 0.8750 9 0.462 14 0.509 1.000 1.125 1.250 1.375 1.500 8777 0.606 12 0.663 0.763 12 0.856 0.969 12 1.07 1.16 12 1.32 6 1.41 12 1.58 Net area calculated using d=d-0.974/N, A = 0.785(d-0.974/N).