What size drill bit do I need?
Pick the thread you are tapping. You get the drill size, a substitute if that bit is not in your set, and the clearance hole.
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Inch tap drill sizes
Each cell is a thread with its tap drill stamped above it, like the holes in a drill index.
3/64"#0-80#53#1-64#53#1-72#50#2-56#50#2-64#47#3-48#45#3-56#43#4-40#42#4-48#38#5-40#37#5-44#36#6-32#33#6-40#29#8-32#29#8-36#25#10-24#21#10-32#16#12-24#14#12-28#13#12-32#71/4-20#31/4-287/32"1/4-32Letter F5/16-18Letter I5/16-249/32"5/16-325/16"3/8-16Letter Q3/8-2411/32"3/8-32Letter U7/16-1425/64"7/16-20Letter Y7/16-2827/64"1/2-1329/64"1/2-2015/32"1/2-2831/64"9/16-1233/64"9/16-1817/32"5/8-1137/64"5/8-1821/32"3/4-1011/16"3/4-1649/64"7/8-913/16"7/8-147/8"1-859/64"1-1263/64"1-1/8-71-3/64"1-1/8-121-7/64"1-1/4-71-11/64"1-1/4-121-7/32"1-3/8-61-19/64"1-3/8-121-11/32"1-1/2-61-27/64"1-1/2-12
Metric tap drill sizes
1.25 mmM1.6 x 0.351.6 mmM2 x 0.42.05 mmM2.5 x 0.452.5 mmM3 x 0.52.9 mmM3.5 x 0.63.3 mmM4 x 0.74.2 mmM5 x 0.85 mmM6 x 16 mmM7 x 16.8 mmM8 x 1.257 mmM8 x 18.5 mmM10 x 1.58.8 mmM10 x 1.259 mmM10 x 110.2 mmM12 x 1.7510.5 mmM12 x 1.510.8 mmM12 x 1.2512 mmM14 x 212.5 mmM14 x 1.514 mmM16 x 214.5 mmM16 x 1.515.5 mmM18 x 2.516.5 mmM18 x 1.517.5 mmM20 x 2.518.5 mmM20 x 1.519.5 mmM22 x 2.520.5 mmM22 x 1.521 mmM24 x 322 mmM24 x 2
Pipe thread (NPT) tap drill sizes
Pilot holes for screws
hardwood 1/16"#2 screwhardwood 5/64"#3 screwhardwood 5/64"#4 screwhardwood 3/32"#5 screwhardwood 7/64"#6 screwhardwood 7/64"#7 screwhardwood 1/8"#8 screwhardwood 9/64"#9 screwhardwood 9/64"#10 screwhardwood 5/32"#12 screwhardwood 11/64"#14 screwlag screw1/4" laglag screw5/16" laglag screw3/8" laglag screw1/2" laglag screw5/8" laglag screw3/4" lag