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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.
| |
| 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 |
|
