THREAD CHART There are six categories of standard taps. We have broken down the drill size recommendations into those six categories which appear below Metric Size Letter Size Metric taps milimeter Thread click here for more info on metric tap sizes Tap Size Drill Size M1.6 x 0.35 1.25mm M2 x 0.4 1/16 M2.5 x 0.45 2.05mm M3 x 0.5 #40 M3 x 0.6 2.5mm M3.5 x 0.6 #33 M4 x 0.7 3.3mm M4 x 0.75 3.4mm M5 x 0.8 4.2mm M5 x 0.9 4.2mm M6 x 1 5mm M6.3 x 1 5.5mm M7 x 1 6.1mm M8 x 1 7.1mm M8 x 1.25 6.7mm M9 x 0.75 8.3mm M9 x 1 8.1mm M9 x 1.25 7.9mm M10 x 1 9.1mm M10 x 1.25 8.9mm M10 x 1.5 8.4mm M11 x 1.50 9.7mm M12 x 1.25 10.9mm M12 x 1.5 10.7mm M12 x 1.75 13/32 M14 x 1.25 12.8mm M14 x 1.5 12.7mm M14 x 2 15/32 M16 x 1.5 14.7mm M16 x 2 35/64 M18 x 1.5 16.8mm M18 x 2.5 15.8mm M20 x 2.5 11/16 M22 x 1.5 20.9mm M24 x 2 22.3mm M24 x 3 53/64 M30 x 3.5 1-3/64 M36 x 4 1-1/4 NC taps National Coarse click here for more info on fractional tap sizes Tap Size Drill Size 1/4-20NC #8 5/16-18NC F 3/8-16NC 5/16 7...