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SAE Tap & Drill Chart

The twist drill bit was invented by Steven A. Morse of East Bridgewater, MA, in 1861. He received U.S. Patent 38,119 for his invention on April 7, 1863. The original method of manufacture was to cut two grooves in opposite sides of a round bar, then to twist the bar to produce the helical flutes. This gave the tool its name.

Nowadays, the drill bit is usually made by rotating the bar while moving it past a grinding wheel to cut the flutes in the same manner as cutting helical gears. Tools recognizable as twist drill bits are currently produced in diameters covering a range from 0.05 mm (0.002") to 100 mm (4"). Lengths up to about 1000 mm (39") are available for use in powered hand tools.

The geometry and sharpening of the cutting edges is crucial to the performance of the bit. Users often throw away small bits that become blunt, and replace them with new bits, because they are inexpensive and sharpening them well is difficult. For larger bits, special grinding jigs are available. A special tool grinder is available for sharpening or reshaping cutting surfaces on twist drills to optimize the drill for a particular material. -Wikipedia

Standard SAE (Society of Automotive Engineers) tap & drill size chart.






Tap Drill







Tap Drill


Coarse Thread Fine Thread
1-64 .0595 No. 53 0-80 .0469 3/64
2-56 .0700 No. 50 1-72 .0595 No. 53
3-48 .0785 No. 47 2-64 .0700 No. 50
4-40 .0890 No. 43 3-56 .0820 No. 45
5-40 .1015 No. 38 4-48 .0935 No. 42
6-32 .1065 No. 36 5-44 .1040 No. 37
8-32 .1360 No. 29 6-40 .1130 No. 33
10-24 .1495 No. 25 8-36 .1360 No. 29
12-24 .1770 No. 16 10-32 .1590 No. 21
1/4-20 .2010 No. 7 12-28 .1820 No. 14
5/16-18 .2570 'F' 1/4-28 .2130 No. 3
3/8-16 .3125 5/16 5/16-24 .2720 'I'
7/16-14 .3680 'U' 3/8-24 .3320 'Q'
1/2-13 .4219 27/64 7/16-20 .3906 25/64
9/16-12 .4844 31/64 1/2-20 .4531 29/64
5/8-11 .5312 17/32 9/16-18 .5156 33/64
3/4-10 .6562 21/32 5/8-18 .5781 37/64
7/8-9 .7656 49/64 3/4-16 .6875 11/16
1"-8 .8750 7/8 7/8-14 .8125 13/16
  1"-14 .9375 59/64

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About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

Copyright  1996 - 2026

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