twist drills

The table below shows the sizes of both U.S. and metric straight shank drills up to ½ inch in diameter. Other shanks (namely, taper shanks) and larger sizes are usually used only in an industrial setting. If you need information on such drills, the most convenient source is the latest edition of

Eric Oberg, ed.
Machinery's Handbook.
New York: Industrial Press.

In the United States, three different systems for designating twist drill sizes are used:

Lengths. The lengths given in the table below are “jobber's lengths.” For some purposes they are too short. Very long twist drills, often called “aircraft drills,” sometimes “electrician's drill,” are available in 6, 12, and even 24-inch lengths.

Points

Ideally the point should be suited to the materials to be drilled. Bits usually come with a 135° split point, although several proprietary designs are also offered.

Material Point angle Chisel angle drawing depicting point angle and chisel edge angle
aluminum 118°–130° 125°–130°
brass 118°–125° 125°–135°
bronze (hard) 118° 115°–125°
copper 100°–130° 125°–135°
plastic 60°–118° 125°–135°
stainless steel 118°–140° 115°–125°
cast iron 90°–118° 115°–125°
cast steel 118° 125°–135°
Drill size Lip relief drawing of lip relief
#80–#61 24°
#60–#41 21°
#40–#31 18°
#30–¼″ 16°
F–1132 14°
S–½″ 12°
3364″–¾″ 10°
4964″ up

U.S. twist drill bit sizes, to ½ inch

Size Diameter Length
inch
Some Uses
U.S. Metric inch mm
97 0.15 0.0059 0.150 ¾  
96 0.16 0.0063 0.160 ¾  
95 0.17 0.0067 0.170 ¾  
94 0.18 0.0071 0.180 ¾  
93 0.20 0.0075 0.200 ¾  
92 0.20 0.0079 0.200 ¾  
91   0.0083 0.211 ¾  
90 0.22 0.0087 0.221 ¾  
89   0.0091 0.231 ¾  
88   0.0095 0.241 ¾  
  0.25 0.0098 0.250 ¾  
87   0.0100 0.254 ¾  
86   0.0105 0.267 ¾  
85 0.28 0.0110 0.280 ¾  
84   0.0115 0.292 ¾  
  0.30 0.0118 0.300 ¾  
83   0.0120 0.305 ¾  
82   0.0125 0.138 ¾  
  0.32 0.0126 0.320 ¾  
81   0.0130 0.330 ¾  
80   0.0135 0.343 ¾  
  0.35 0.0138 0.350 ¾  
79   0.0145 0.368 ¾  
  0.38 0.0150 0.380 ¾  
1/64   0.0156 0.396 ¾ Pilot hole in softwood for #0 wood screw.
  0.40 0.0157 0.400 ¾  
78   0.0160 0.406  
  0.42 0.0165 0.420  
  0.45 0.0177 0.450  
77   0.0180 0.457  
  0.48 0.0189 0.480  
  0.50 0.0197 0.500  
76   0.0200 0.508  
75   0.0210 0.533 1  
  0.55 0.0217 0.550 1  
74   0.0225 0.572 1  
  0.60 0.0236 0.600 1 ⅛  
73   0.0240 0.610 1 ⅛  
72   0.0250 0.635 1 ⅛  
  0.65 0.0256 0.650  
71   0.0260 0.660 Tap for 000-120.
  0.70 0.0276 0.700  
70   0.0280 0.711  
69   0.0292 0.742 1 ⅜  
  0.75 0.0295 0.750 1 ⅜  
68   0.0310 0.787 1 ⅜  
ยน⁄32   0.0312 0.792 1 ⅜ Pilot hole in softwood for #1 and #2 wood screw;
pilot hole in hardwood for #0 and #1 wood screw.
  0.80 0.0315 0.800 1 ⅜  
67   0.0320 0.813 1 ⅜  
66   0.0330 0.838 1 ⅜  
  0.85 0.0335 0.850  
65   0.0350 0.889 Close fit clearance hole for #000 screw;
tap for 00-90.
  0.90 0.0354 0.899  
64   0.0360 0.914  
63   0.0370 0.940  
  0.95 0.0374 0.950  
62   0.0380 0.965 Free fit clearance hole for #000 screw.
61   0.0390 0.991 1 ⅝  
  1.00 0.0394 1.00 1 ⅝  
60   0.0400 1.016 1 ⅝  
59   0.0410 1.041 1 ⅝  
  1.05 0.0413 1.050 1 ⅝  
58   0.0420 1.067 1 ⅝  
57   0.0430 1.092  
  1.10 0.0433 1.100  
  1.15 0.0453 1.150 1 ¾  
56   0.0465 1.181  
3/64   0.0469 1.191 Close fit clearance hole for #00 screw;
tap for 0-80; 
pilot hole in softwood for # 3 & #4 wood screw;
pilot hole in hardwood for #2 wood screw.
  1.20 0.0472 1.200 1⅞  
  1.25 0.0492 1.250 1⅞  
  1.30 0.0512 1.300 1⅞  
55   0.0520 1.321 1⅞  Free fit clearance hole for #00 screw.
  1.35 0.0531 1.350 1⅞  
54   0.0550 1.397 1⅞  
  1.40 0.0551 1.400 1⅞  
  1.45 0.0571 1.450 1⅞  
  1.50 0.0591 1.500 1⅞  
53   0.0595 1.511 1⅞ Tap for 1-64, 1-72.
  1.55 0.0610 1.550 1⅞  
1/16   0.0625 1.588 1⅞ Clearance hole for #0 wood screw; 
pilot hole in softwood for #5 wood screw.
  1.60 0.0630 1.600 1⅞  
52   0.0635 1.613 1⅞ Close fit clearance hole for #0 screw;
tap for M2.
  1.65 0.0650 1.650 2  
  1.70 0.0669 1.700 2  
51   0.0670 1.702 2  
  1.75 0.0689 1.750 2  
50   0.0700 1.778 2 Free fit clearance hole for #0 screw;
tap for 2-56, 2-64.
  1.80 0.0709 1.800 2  
  1.85 0.0728 1.850 2  
49   0.0730 1.854 2  
  1.90 0.0748 1.900 2  
48   0.0760 1.930 2 Close fit clearance hole for #1 screw.
  1.95 0.0768 1.950 2  
564   0.0781 1.984 2 Clearance hole for #1 wood screw; pilot hole in softwood
for #8 & #9 wood screw and in hardwood for #5 & #6 wood screw.
47   0.0785 1.994 2  
  2.00 0.0787 2.000 2  
  2.05 0.0807 2.050 2 ⅛  
46   0.0810 2.057 2 ⅛ Close fit clearance hole for M2 screw; free 
fit clearance hole for #1 screw; tap for M2.5.
45   0.0820 2.083 2 ⅛  
  2.10 0.0827 2.100 2 ⅛  
  2.15 0.0846 2.150 2 ⅛  
44   0.0860 2.184 2 ⅛ Free fit clearance hole for M2 screw; tap for 4-36.
  2.20 0.0866 2.200  
  2.25 0.0886 2.250  
43   0.0890 2.261 Close fit clearance hole for #2 screw; tap for 4-40.
  2.30 0.0906 2.300  
  2.35 0.0925 2.350  
42   0.0935 2.375 Tap for 4-48.
3/32   0.0938 2.383 Clearance hole for #2 wood screw; 
pilot hole in softwood for #10 & #12 wood screw; 
pilot hole in hardwood for #7 & #8 wood screw.
  2.40 0.0945 2.400 2 ⅜  
41   0.0960 2.438 2 ⅜ Free fit clearance hole for #2 screw.
  2.45 0.0965 2.450 2 ⅜  
40   0.0980 2.489 2 ⅜ Tap for M3.
  2.50 0.0984 2.500 2 ⅜  
39   0.0995 2.527 2 ⅜  
38   0.1015 2.578 Tap for 5-40.
  2.60 0.1024 2.600  
37   0.1040 2.642 Tap for 5-44.
  2.70 0.1063 2.700  
36   0.1065 2.705 Close fit clearance hole for M2.5 screw; tap for 6-32.
7/64   0.1094 2.779 2 ⅝ Clearance hole for #3 & #4 wood screw; 
pilot hole in softwood for #12 & #14 wood screw;
pilot hole for #9 & #10 wood screw in hardwood.
35   0.1100 2.794 2 ⅝  
  2.80 0.1102 2.800 2 ⅝  
34   0.1110 2.819 2 ⅝  
33   0.1130 2.870 2 ⅝ Tap for 6-40.
  2.90 0.1142 2.900  
32   0.1160 2.946 Close fit clearance hole for #4 screw.
  3.00 0.1181 3.000  
31   0.1200 3.048 Close fit clearance hole for M3 screw; 
free fit clearance hole for M2.5 screw.
  3.10 0.1220 3.100 2 ¾  
  0.1250 3.175 2 ¾ clearance hole for #5 wood screw; Pilot hole in hardwood
for #11 & #12 wood screw 
  3.20 0.1260 3.200  
30   0.1285 3.264 Close fit clearance hole for #5 screw; free
fit clearance hole for #4 screw
  3.30 0.1299 3.300 2⅞  
  3.40 0.1339 3.400 2⅞  
29   0.1360 3.454 2⅞ Tap for M4, 8-32, 8-36 screws.
  3.50 0.1378 3.500 2⅞  
28   0.1405 3.569 2⅞  
9/64   0.1406 3.571 2⅞ Free fit clearance hole for M3 screw; 
clearance hole for #6 wood screw; 
pilot hole in softwood for #16 & #18 wood screw;
Pilot hole in hardwood for #14 wood screw.
  3.60 0.1417 3.600 3  
27   0.1440 3.658 3 Close fit clearance hole for #6 screw;
free fit clearance hole for #5 screw.
  3.70 0.1457 3.700 3  
26   0.1470 3.734 3  
25   0.1495 3.797 3 Free fit clearance hole for #6 screw;
tap for 10-24 screw.
  3.80 0.1496 3.800 3  
24   0.1520 3.861 3 ⅛  
  3.90 0.1535 3.900 3 ⅛  
23   0.1540 3.912 3 ⅛  
5/32   0.1562 3.967 3 ⅛ Clearance hole for #7 wood screw; 
pilot hole in hardwood for #16 wood screw
22   0.1570 3.988 3 ⅛  
  4.00 0.1575 4.000  
21   0.1590 4.039 Tap for 10-32 screw.
20   0.1610 4.089  
  4.10 0.1614 4.100  
  4.20 0.1654 4.200  
19   0.1660 4.216  
  4.30 0.1693 4.300  
18   0.1695 4.305 Close fit clearance hole for M4, #8 screws;
tap for M5.
11/64   0.1719 4.366 Clearance hole for #8 wood screw; 
pilot hole in softwood for #20 wood screw.
17   0.1730 4.394 3 ⅜  
  4.40 0.1732 4.400 3 ⅜  
16   0.1770 4.496 3 ⅜  
  4.50 0.1772 4.500 3 ⅜  
15   0.1800 4.572 3 ⅜  
  4.60 0.1811 4.600 3 ⅜  
14   0.1820 4.623 3 ⅜ Tap for 12-24 screw.
13 4.70 0.1850 4.700  
3/16   0.1875 4.762 Clearance hole for #9 & #10 wood screw;
pilot hole in hardwood for #18 wood screw;
pilot hole in softwood for #24 wood screw.
12 4.80 0.1890 4.800 31/2  
11   0.1910 4.851 31/2  
  4.90 0.1929 4.900 3 ⅝  
10   0.1935 4.915 3 ⅝  
9   0.1960 4.978 3 ⅝ Close fit clearance hole for #10 screw.
  5.00 0.1969 5.000 3 ⅝  
8   0.1990 5.054 3 ⅝  
  5.10 0.2008 5.100 3 ⅝  
7   0.2010 5.105 3 ⅝ Free fit clearance hole for #10 screw;
tap for ¼-20 screw.
13/64   0.2031 5.159 3 ⅝  
6   0.2040 5.182 3 ¾ Tap for M6.
  5.20 0.2047 5.200  
5   0.2055 5.220 3 ¾  
  5.30 0.2087 5.300 3 ¾  
4   0.2090 5.309 3 ¾ Close fit clearance hole for M5 screw.
  5.40 0.2126 5.400 3 ¾  
3   0.2130 5.410 3 ¾ Tap for ¼-28.
  5.50 0.2165 5.500 3 ¾  
732   0.2188 5.558 3 ¾ Clearance hole for #12 wood screw:
pilot hole in hardwood for #24 wood screw.
  5.60 0.2205 5.600 3⅞  
2   0.2210 5.613 3⅞  
  5.70 0.2244 5.700 3⅞  
1   0.2280 5.791 3⅞ Free fit clearance hole for M5 screw
  5.80 0.2283 5.800 3⅞  
  5.90 0.2323 5.600 3⅞  
A   0.2340 5.944 3⅞  
15/64   0.2344 5.954 3⅞  
  6.00 0.2362 6.000 4  
B   0.2380 6.045 4  
  6.10 0.2402 6.100 4  
C   0.2420 6.147 4  
  6.20 0.2441 6.200 4  
D   0.2460 6.248 4  
  6.30 0.2480 6.300 4  
E, ¼   0.2500 6.350 4 Close fit clearance hole for M6 screw;
clearance hole for #14 wood screw.
  6.40 0.2520 6.400 4 ⅛  
  6.50 0.2559 6.500 4 ⅛  
F   0.2570 6.528 4 ⅛ Close fit clearance hole for ¼" screw;
tap for 5/16-18 screw.
  6.60 0.2598 6.600 4 ⅛  
G   0.2610 6.629 4 ⅛ Free fit clearance hole for M6 screw.
  6.70 0.2638 6.700 4 ⅛  
17/64   0.2656 6.746 4 ⅛ Clearance hole for #16 wood screw.
H   0.2660 6.756 4 ⅛ Free fit clearance hole for ¼" screw.
  6.80 0.2677 6.800 4 ⅛  
  6.90 0.2717 6.900 4 ⅛  
I   0.2720 6.909 4 ⅛ Tap for 5/16-20 & M8 screws.
  7.00 0.2756 7.000 4 ⅛  
J   0.2770 7.036 4 ⅛  
  7.10 0.2795 7.100  
K   0.2810 7.137  
9/32   0.2812 7.142  
  7.20 0.2835 7.200  
  7.30 0.2874 7.300  
L   0.2900 7.366  
  7.40 0.2913 7.400 4 ⅜  
M   0.2950 7.493 4 ⅜  
  7.50 0.2953 7.500 4 ⅜  
19/64   0.2969 7.541 4 ⅜ Clearance hole for #18 wood screw.
  7.60 0.2992 7.600 4 ⅜  
N   0.3020 7.671 4 ⅜  
  7.70 0.3031 7.700  
  7.80 0.3071 7.800  
  7.90 0.3110 7.900  
5/16   0.3125 7.938 Tap for ⅜-16 screw.
  8.00 0.3150 8.000  
O   0.3160 8.026  
  8.10 0.3189 8.100 4 ⅝  
  8.20 0.3228 8.200 4 ⅝  
P   0.3230 8.204 4 ⅝ Close fit clearance hole for 5/16″, M8 screws.
  8.30 0.3268 8.300 4 ⅝  
21/64   0.3281 8.334 4 ⅝ Clearance hole for #20 wood screw.
8.40 0.3307 8.400  
Q   0.3320 8.433 Free fit clearance hole for 5/16", M8 screws;
tap for ⅜-24 screw.
  8.50 0.3346 8.500  
  8.60 0.3386 8.600  
R   0.3390 8.611  
  8.70 0.3425 8.700  
11/32   0.3438 8.733 Tap for M10.
  8.80 0.3465 8.800 4⅞  
S   0.3480 8.839 4⅞  
  8.90 0.3504 8.900 4⅞  
  9.00 0.3543 9.000 4⅞  
T   0.3580 9.093 4⅞  
  9.10 0.3583 9.100 4⅞  
23/64   0.3594 9.129 4⅞  
  9.20 0.3622 9.200 5  
  9.30 0.3661 9.300 5  
U   0.3680 9.347 5  
  9.40 0.3701 9.400 5  
  9.50 0.3740 9.500 5  
  0.3750 9.525 5 Clearance hole for #24 wood screw.
V   0.3770 9.576 5  
  9.60 0.3780 9.600 5 ⅛  
  9.70 0.3819 9.700 5 ⅛  
  9.80 0.3858 9.800 5 ⅛  
W   0.3860 9.804 5 ⅛ Close fit clearance hole for ⅜" screw.
  9.90 0.3898 9.900 5 ⅛  
25/64   0.3906 9.921 5 ⅛  
  10.00 0.3937 10.00 5 ⅛  
X   0.3970 10.084 5 ⅛ Free fit clearance hole for ⅜" screw.
  10.20 0.4016 10.200  
Y   0.4040 10.262  
13/32   0.4062 10.317 Close fit clearance hole for M10 screw.
Z   0.4130 10.490 Tap for M12 screw.
  10.50 0.4134 10.500  
27/64   0.4219 10.716 5 ⅜ Free fit clearance hole for M10 screw;
tap for ½-13 screw.
  10.80 0.4252 10.800  
  11.00 0.4331 11.000  
7/16   0.4375 11.112  
  11.20 0.4409 11.200 5 ⅝  
  11.50 0.4528 11.500 5 ⅝  
29/64   0.4531 11.509 5 ⅝ Tap for ½-20 screw.
  11.80 0.4646 11.800  
15/32   0.4688 11.908  
  12.00 0.4724 12.000 5⅞  
  12.20 0.4803 12.200 5⅞  
31/64   0.4844 12.304 5⅞ Close fit clearance hole for M12 screw.
  12.50 0.4921 12.500 6  
½   0.500 12.700 6 Free fit clearance hole for M12 screw.

ANSI standard B94.11M-1979.

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