Taper Length Drill Dimensions

U.S. taper length twist "drill bit" sizes

Size Diameter Flute Length Overall Length
U.S. Metric (mm) inch mm inch inch
1.00 0.0394 1.00 1 1/8 2 1/4
60 0.0400 1.016 1 1/8 2 1/4
59 0.0410 1.041 1 1/8 2 1/4
1.05 0.0413 1.050 1 1/8 2 1/4
58 0.0420 1.067 1 1/8 2 1/4
57 0.0430 1.092 1 1/8 2 1/4
1.10 0.0433 1.100 1 1/8 2 1/4
1.15 0.0453 1.150 1 1/8 2 1/4
56 0.0465 1.181 1 1/8 2 1/4
3/64 0.0469 1.191 1 1/8 2 1/4
1.20 0.0472 1.200 1 3/4 3
1.25 0.0492 1.250 1 3/4 3
1.30 0.0512 1.300 1 3/4 3
55 0.0520 1.321 1 3/4 3
1.35 0.0531 1.350 1 3/4 3
54 0.0550 1.397 1 3/4 3
1.40 0.0551 1.400 1 3/4 3
1.45 0.0571 1.450 1 3/4 3
1.50 0.0591 1.500 1 3/4 3
53 0.0595 1.511 1 3/4 3
1.55 0.0610 1.550 1 3/4 3
1/16 0.0625 1.588 1 3/4 3
1.60 0.0630 1.600 2 3 3/4
52 0.0635 1.613 2 3 3/4
1.65 0.0650 1.650 2 3 3/4
1.70 0.0669 1.700 2 3 3/4
51 0.0670 1.702 2 3 3/4
1.75 0.0689 1.750 2 3 3/41
50 0.0700 1.778 2 3 3/4
1.80 0.0709 1.800 2 3 3/4
1.85 0.0728 1.850 2 3 3/4
49 0.0730 1.854 2 3 3/4
1.90 0.0748 1.900 2 3 3/4
48 0.0760 1.930 2 3 3/4
1.95 0.0768 1.950 2 3 3/4
5/64 0.0781 1.984 2 3 3/4
47 0.0785 1.994 2 1/4 4 1/4
2.00 0.0787 2.000 2 1/4 4 1/4
2.05 0.0807 2.050 2 1/4 4 1/4
46 0.0810 2.057 2 1/4 4 1/8
45 0.0820 2.083 2 1/4 4 1/4
2.10 0.0827 2.100 2 1/4 4 1/4
2.15 0.0846 2.150 2 1/4 4 1/4
44 0.0860 2.184 2 1/4 4 1/4
2.20 0.0866 2.200 2 1/4 4 1/4
2.25 0.0886 2.250 2 1/4 4 1/4
43 0.0890 2.261 2 1/4 4 1/4
2.30 0.0906 2.300 2 1/4 4 1/4
2.35 0.0925 2.350 2 1/4 4 1/4
42 0.0935 2.375 2 1/4 4 1/4
3/32 0.0938 2.383 2 1/4 4 1/4
2.40 0.0945 2 1/2 2 3/8 4 5/8
41 0.0960 2.438 2 1/2 4 5/8
2.45 0.0965 2.450 2 1/2 4 5/8
40 0.0980 2.489 2 1/2 4 5/8
2.50 0.0984 2.500 2 1/2 4 5/8
39 0.0995 2.527 2 1/2 4 5/8
38 0.1015 2.578 2 1/2 4 5/8
2.60 0.1024 2.600 2 1/2 4 5/8
37 0.1040 2.642 2 1/2 4 5/8
2.70 0.1063 2.700 2 1/2 4 5/8
36 0.1065 2.705 2 1/2 4 5/8
7/64 0.1094 2.779 2 1/2 4 5/8
35 0.1100 2.794 2 3/4 5 1/8
2.80 0.1102 2.800 2 3/4 5 1/8
34 0.1110 2.819 2 3/4 5 1/8
33 0.1130 2.870 2 3/4 5 1/8
2.90 0.1142 2.900 2 3/4 5 1/8
32 0.1160 2.946 2 3/4 5 1/8
3.00 0.1181 3.000 2 3/4 5 1/8
31 0.1200 3.048 2 3/4 5 1/8
3.10 0.1220 3.100 2 3/4 5 1/8
1/8 0.1250 3.0175 2 3/4 5 1/8
3.20 0.1260 3.200 3 5 3/8
30 0.1285 3.264 3 5 3/8
3.30 0.1299 3.300 3 5 3/8
3.40 0.1339 3.400 3 5 3/8
29 0.1360 3.454 3 5 3/8
3.50 0.1378 3.500 3 5 3/8
28 0.1405 3.569 3 5 3/8
9/64 0.1406 3.571 3 5 3/8
3.60 0.1417 3.600 3 5 3/8
27 0.1440 3.658 3 5 3/8
3.70 0.1457 3.700 3 5 3/8
26 0.1470 3.734 3 5 3/8
25 0.1495 3.797 3 5 3/8
3.80 0.1496 3.800 3 5 3/8
24 0.1520 3.861 3 5 3/8
3.90 0.1535 3.900 3 5 3/8
23 0.1540 3.912 3 5 3/8
5/32 0.1562 3.967 3 5 3/8
22 0.1570 3.988 3 3/8 5 3/4
4.00 0.1575 4.000 3 3/8 5 3/4
21 0.1590 4.039 3 3/8 5 3/4
20 0.1610 4.089 3 3/8 5 3/4
4.10 0.1614 4.100 3 3/8 5 3/4
4.20 0.1654 4.200 3 3/8 5 3/4
19 0.1660 4.216 3 3/8 5 3/4
4.30 0.1693 4.300 3 3/8 5 3/4
18 0.1695 4.305 3 3/8 5 3/4
11/64 0.1719 4.366 3 3/8 5 3/4
17 0.1730 4.394 3 3/8 5 3/4
4.40 0.1732 4.400 3 3/8 5 3/4
16 0.1770 4.496 3 3/8 5 3/4
4.50 0.1772 4.500 3 3/8 5 3/4
15 0.1800 4.572 3 3/8 5 3/4
4.60 0.1811 4.600 3 3/8 5 3/4
14 0.1820 4.623 3 3/8 5 3/4
13 4.70 0.1850 4.700 3 3/8 5 3/4
3/16 0.1875 4.762 3 3/8 5 3/4
12 4.80 0.1890 4.800 3 5/8 6
11 0.1910 4.851 3 5/8 6
4.90 0.1929 4.900 3 5/8 6
10 0.1935 4.915 3 5/8 6
9 0.1960 4.978 3 5/8 6
5.00 0.1969 5.000 3 5/8 6
8 0.1990 5.054 3 5/8 6
5.10 0.2008 5.100 3 5/8 6
7 0.2010 5.105 3 5/8 6
13/64 0.2031 5.159 3 5/8 6
6 0.2040 5.182 3 5/8 6
5.20 0.2047 5.200 3 5/8 6
5 0.2055 5.220 3 5/8 6
5.30 0.2087 5.300 3 5/8 6
4 0.2090 5.309 3 5/8 6
5.40 0.2126 5.400 3 5/8 6
3 0.2130 5.410 3 5/8 6
5.50 0.2165 5.500 3 5/8 6
7/32 0.2188 5.558 3 5/8 6
5.60 0.2205 5.600 3 3/4 6 1/8
2 0.2210 5.613 3 3/4 6 1/8
5.70 0.2244 5.700 3 3/4 6 1/8
1 0.2280 5.791 3 3/4 6 1/8
5.80 0.2283 5.800 3 3/4 6 1/8
5.90 0.2323 5.600 3 3/4 6 1/8
A 0.2340 5.944 nbsp;
15/64 0.2344 5.954 3 3/4 6 1/8
6.00 0.2362 6.000 3 3/4 6 1/8
B 0.2380 6.045
6.10 0.2402 6.100 3 3/4 6 1/8
C 0.2420 6.147
6.20 0.2441 6.200 3 3/4 6 1/8
D 0.2460 6.248
6.30 0.2480 6.300 3 3/4 6 1/8
E, 1/4 0.2500 6.350 3 3/4 6 1/8
6.40 0.2520 6.400 3 7/8 6 1/4
6.50 0.2559 6.500 3 7/8 6 1/4
F 0.2570 6.528
6.60 0.2598 6.600
G 0.2610 6.629
6.70 0.2638 6.700
17/64 0.2656 6.746 3 7/8 6 1/4
H 0.2660 6.756
6.80 0.2677 6.800 3 7/8 6 1/4
6.90 0.2717 6.900
I 0.2720 6.909
7.00 0.2756 7.000 3 7/8 6 1/4
J 0.2770 7.036
7.10 0.2795 7.100
K 0.2810 7.137
9/32 0.2812 7.142 3 7/8 6 1/4
7.20 0.2835 7.200 4 6 3/8
7.30 0.2874 7.300
L 0.2900 7.366
7.40 0.2913 7.400
M 0.2950 7.493
7.50 0.2953 7.500 4 6 3/8
19/64 0.2969 7.541 4 6 3/8
7.60 0.2992 7.600
N 0.3020 7.671
7.70 0.3031 7.700
7.80 0.3071 7.800 4 6 3/8
7.90 0.3110 7.900
5/16 0.3125 7.938 4 6 3/8
8.00 0.3150 8.000 4 1/8 6 1/2
O 0.3160 8.026
8.10 0.3189 8.100
8.20 0.3228 8.200 4 1/8 6 1/2
P 0.3230 8.204
8.30 0.3268 8.300
21/64 0.3281 8.334 4 1/8 6 1/2
8.40 0.3307 8.400 /
Q 0.3320 8.433
8.50 0.3346 8.500 4 1/8 6 1/2
8.60 0.3386 8.600
R 0.3390 8.611
8.70 0.3425 8.700
11/32 0.3438 8.733 4 1/8 6 1/2
8.80 0.3465 8.800 4 1/4 6 3/4
S 0.3480 8.839
8.90 0.3504 8.900
9.00 0.3543 9.000 4 1/4 6 3/4
T 0.3580 9.093
9.10 0.3583 9.100
23/64 0.3594 9.129 4 1/4 6 3/4
9.20 0.3622 9.200 4 1/4 6 3/4
9.30 0.3661 9.300
U 0.3680 9.347
9.40 0.3701 9.400
9.50 0.3740 9.500 4 1/4 6 3/4
3/8 0.3750 9.525 4 1/4 6 3/4
V 0.3770 9.576
9.60 0.3780 9.600
9.70 0.3819 9.700
9.80 0.3858 9.800 4 3/8 7
W 0.3860 9.804
9.90 0.3898 9.900
25/64 0.3906 9.921 4 3/8 7
10.00 0.3937 10.00 4 3/8 7
X 0.3970 10.084
10.20 0.4016 10.200 4 3/8 7
Y 0.4040 10.262
13/32 0.4062 10.317 4 3/8 7
Z 0.4130 10.490
10.50 0.4134 10.500 4 5/8 7 1/4
27/64 0.4219 10.716 4 5/8 7 1/4
10.80 0.4252 10.800 4 5/8 7 1/4
11.00 0.4331 11.000 4 5/8 7 1/4
7/16 0.4375 11.112 4 5/8 7 1/4
11.20 0.4409 11.200 4 3/4 7 1/2
11.50 0.4528 11.500 4 3/4 7 1/2
29/64 0.4531 11.509 4 3/4 7 1/2
11.80 0.4646 11.800 4 3/4 7 1/2
15/32 0.4688 11.908 4 3/4 7 1/2
12.00 0.4724 12.000 4 3/4 7 3/4
12.20 0.4803 12.200 4 3/4 7 3/4
31/64 0.4844 12.304 4 3/4 7 3/4
12.50 0.4921 12.500 4 3/4 7 3/4
1/2 0.500 12.700 4 3/4 7 3/4

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This chart covers only the typical taper length drill specifications. There are reduced shank and custom shank drills on the market which may differ. Taper length drills are often used in drill press machines, automatic self-feeder drills, multiple spindle drilling heads, etc.

Why do my tools wear quickly or break?

Note that excessive tool wear or breakage is often caused by:

  • Improper surface speeds
  • Improper feed rates
  • Improper cutting tool type or material (HSS vs TiN vs Carbide, etc.)
  • Dull tooling
  • Hard spots in the material such as scale, silica, imperfections, etc.
  • Improper coolant or lubricant type
  • Inadequate coolant or lubricant (overall for chip removal, rubbing, etc.)
  • Inadequate coolant or lubricant (at the tip of the tooling)
  • The tool is not rigid enough (try drill bushings or guides, guide rods on the drilling machine, etc.)
  • Too deep of a cut without proper chip removal – Chip packing (try peck drilling, air blast or coolant through the tool options, etc.)
  • Tools that were manufactured or sharpened incorrectly. (watch those clearance, rake and lip angles as well as rough surfaces, etc.)

Calculating or estimating cycle time when drilling

We can help you lower your cycle time when drilling holes in a part or multiple parts. Generally, this is the calculation we use to figure out the time it will take to perform a process:

DEPTH divided by FEED = ROTATIONS.
ROTATIONS divided by RPM = MINUTES.
MINUTES multiplied by 60 = SECONDS it takes for the process.

(DEPTH = 30% of the diameter of the tool plus the thickness of the material)
Add in stroke up to product time
Add in stroke back to home time
Add in clamp and unclamp time
Add in any human factors, etc.
Add in time for potentially dull tooling, etc.
Add in time for less than adequate machine thrust, etc.

We use the following charts to estimate these numbers: