Taps are cutting tools used to create screw threads inside a hole, while drill bits are used to create the initial hole before tapping. This chart provides guidance on the correct tap and drill bit sizes to use for different thread sizes, ensuring that the threads are of the correct size and pitch and that they will fit the intended screw or bolt.

Machine Screw Size Number of Threads Per Inch (TPI) Major Diameter Minor Diameter Tap drills Clearance Drill 75% Thread for Aluminum, Brass, & Plastics 50% Thread for Steel, Stainless, & Iron Close Fit Free Fit Drill Size Decimal Equiv. Drill Size Decimal Equiv. Drill Size Decimal Equiv. Drill Size Decimal Equiv. 0 80 .0600 .0447 3/64 .0469 55 .0520 52 .0635 50 .0700 1 64 .0730 .0538 53 .0595 1/16 .0625 48 .0760 46 .0810 72 .0560 53 .0595 52 .0635         2 56 .0860 .0641 50 .0700 49 .0730 43 .0890 41 .0960 64 .0668 50 .0700 48 .0760         3 48 .0900 .0734 47 .0785 44 .0860 37 .1040 35 .1100 56 .0771 45 .0820 43 .0890         4 40 1120 .0813 43 .0890 41 .0960 32 .1160 30 .1285 48 .0864 42 .0935 40 .0980         5 40 1250 .0943 38 .1015 7/64 .1094 30 .1285 29 .1360 44 .0971 37 .1040 35 .1100         6 32 .1380 .0997 36 .1065 32 .1160 27 .1440 25 .1495 40 .1073 33 .1130 31 .1200         8 32 .1640 .1257 29 .1360 27 .1440 18 .1695 16 .1770 36 .1299 29 .1360 26 .1470         10 24 1900 .1389 25 .1495 20 .1610 9 .1960 7 .2010 32 .1517 21 .1590 18 .1695         12 24 0.216 .1649 16 .1770 12 .1890 2 .2210 1 .2280 28 .1722 14 .1820 10 .1935 32 .1777 13 .1850 9 .1960 1/4 20 0.2500 .1887 7 .2010 7/32 .2188 F .2570 H .2260 28 .2062 3 .2130 1 .2280 32 .2117 7/32 .2188 1 .2280 5/16 18 0.313 .2443 F .2570 J .2770 P .3230 Q .3320 24 .2614 I .2720 9/32 .2812 32 .2742 9/32 .2812 L .2900 3/8 16 .3750 .2983 5/16 .3125 Q .3320 W .3860 X .3970 24 .3239 Q .3320 S 3480 32 .3367 11/32 .3438 T .3580 7/16 14 0.438 .3499 U .3680 25/64 .3906 29/64 .4531 15/32 .4687 20 .3762 25/64 .3906 13/32 .4062 28 .3937 Y .4040 Z .4130 1/2 13 0.500 .4056 27/64 .4219 29/64 .4531 33/64 .5156 17/32 .5312 20 .4387 29/64 .4531 15/32 .4688 28 .4562 15/32 .4688 15/32 .4688 9/16 12 .5625 .4603 31/64 .4844 33/64 .5156 37/64 .5781 19/32 .5938 18 .4943 33/64 .5156 17/32 .5312 24 .5514 33/64 .5156 17/32 .5312 5/8 11 0.625 .5135 17/32 .5312 9/16 .5625 41/64 .6406 21/32 .6562 18 .5568 37/64 .5781 19/32 .5938 24 .5739 37/64 .5781 19/32 .5938 11/16 24 .5875 .6364 41/64 .6406 21/32 .6562 45/64 .7031 23/32 .7188 3/4 10 0.75 .6273 21/32 .6562 11/16 .6875 49/64 .7656 25/32 .7812 16 .6733 11/16 .6875 45/64 .7031 20 .6887 45/64 .7031 23/32 .7188 13/16 20 .8125 .7512 49/64 .7656 25/32 .7812 53/64 .8281 27/32 .8438 7/8 9 0.875 .7387 49/64 .7656 51/64 .7969 57/64 .8906 29/32 .9062 14 .7874 13/16 .8125 53/64 .8281 20 .8137 53/64 .8281 27/32 .8438 15/16 20 .9375 .8762 57/64 .8906 29/32 .9062 61/64 .9531 31/32 .9688 1 8 1 .8466 7/8 .8750 59/64 .9219 1-1/64 1.0156 1-1/32 1.0313 12 .8978 15/16 .9375 61/64 .9531 20 .9387 61/64 .9531 31/32 .9688 1-1/16 18 1.0625 .9943 1.000 1.000 1-1/64 1.1056 1-5/64 1.0781 1-3/32 1.0938 1-1/8 7 1.125 .9497 63/64 .9844 1-1/32 1.0313 1-9/64 1.1406 1-5/32 1.1562 12 1.0228 1-3/64 1.0469 1-5/64 1.0781 18 1.0568 1-1/16 1.0625 1-5/64 1.0781 1-3/16 18 1.1875 1.1193 1-1/8 1.1250 1-9/64 1.1406 1-13/64 1.2031 1-7/32 1.2188

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The tap and drill bit chart lists the next parameters: Number of Threads Per Inch (TPI), Major Diameter, Minor Diameter, Tap Drill size, Clearance Drill size, Decimal Equivalents for Tap drills, Decimal Equivalents for Clearance Drills, Close Fit size, Free Fit size, and the percentage of thread engagement. The pitch diameter is the diameter at which the width of the thread and the width of the groove between threads are equal. The percentage of thread engagement is the percentage of the length of the screw that will be engaged in the threaded hole.

This technical reference document provides information on the appropriate tap and drill bit sizes to use when creating threaded holes in various materials such as Stainless Steel, Steel, Iron, Brass, Aluminum, and Plastics.