Drill sizes assume approximately 75% thread engagement. For tougher materials or
through-tapped holes in thicker stock, drop one size larger. For very soft
materials (brass, aluminum), drop one size smaller.
UNC (coarse)
Size TPI Drill Dec. (in) #0-80 80 3/64 0.0469 #1-64 64 #53 0.0595 #2-56 56 #50 0.0700 #3-48 48 #47 0.0785 #4-40 40 #43 0.0890 #5-40 40 #38 0.1015 #6-32 32 #36 0.1065 #8-32 32 #29 0.1360 #10-24 24 #25 0.1495 #12-24 24 #16 0.1770 1/4-20 20 #7 0.2010 5/16-18 18 F 0.2570 3/8-16 16 5/16 0.3125 7/16-14 14 U 0.3680 1/2-13 13 27/64 0.4219 9/16-12 12 31/64 0.4844 5/8-11 11 17/32 0.5313 3/4-10 10 21/32 0.6563 7/8-9 9 49/64 0.7656 1-8 8 7/8 0.8750
UNF (fine)
Size TPI Drill Dec. (in) #0-80 80 3/64 0.0469 #1-72 72 #53 0.0595 #2-64 64 #50 0.0700 #3-56 56 #45 0.0820 #4-48 48 #42 0.0935 #5-44 44 #37 0.1040 #6-40 40 #33 0.1130 #8-36 36 #29 0.1360 #10-32 32 #21 0.1590 #12-28 28 #14 0.1820 1/4-28 28 #3 0.2130 5/16-24 24 I 0.2720 3/8-24 24 Q 0.3320 7/16-20 20 25/64 0.3906 1/2-20 20 29/64 0.4531 9/16-18 18 33/64 0.5156 5/8-18 18 37/64 0.5781 3/4-16 16 11/16 0.6875 7/8-14 14 13/16 0.8125 1-12 12 59/64 0.9219
Metric coarse
Size Pitch (mm) Drill (mm) M1.6 0.35 1.25 M2 0.40 1.60 M2.5 0.45 2.05 M3 0.50 2.50 M4 0.70 3.30 M5 0.80 4.20 M6 1.00 5.00 M8 1.25 6.80 M10 1.50 8.50 M12 1.75 10.20 M14 2.00 12.00 M16 2.00 14.00 M20 2.50 17.50