TM 9-254 Figure 5-3. Typical Screw Thread Form Table 5-10.  Basic Coarse Thread Dimensions and Tap Drill Sizes - American Machine Screw Commercial Decimal Nominal size Outside Pitch Root tap drill to equivalent diameter diameter diameter produce approx of tap Inch Threads (in.) (in.) (in.) 75 percent drill per inch full thread 0-80 0.0600 0.0519 0.0438 3/64 0.0469 1-56 .0730 .0614 .0498 54 .0550 64 .0730 .0629 .0527 53 .0595 72 .0730 .0640 .0550 53 .0595 2-56 .0860 .0744 .0628 50 .0700 64 .0860 .0759 .0657 50 .0700 3-48 .0990 .0855 .0719 47 .0785 56 .0990 .0874 .0758 45 .0820 4-32 .1120 .0917 .0714 45 .0820 36 .1120 .0940 .0759 44 .0860 40 .0020 .0958 .0795 43 .0890 48 .1120 .0985 .0849 42 .0935 5-22