# List of drill and tap sizes

(Redirected from Drill chart)
Schematic of a machine tap

Below is a comprehensive drill and tap size chart for all drills and taps, imperial and metric, up to 36.5 millimetres (1.44 in) in diameter.

In manufactured parts, holes with female screw threads are often needed; they accept male screws to facilitate the building and fastening of a finished assembly. One of the most common ways to produce such threaded holes is to drill a hole of appropriate size with a drill bit and then tap it with a tap. Each standard size of female screw thread has one or several corresponding drill bit sizes that are within the range of appropriate size—slightly larger than the minor diameter of the mating male thread, but smaller than its pitch and major diameters. Such an appropriately sized drill is called a tap drill for that size of thread, because it is a correct drill to be followed by the tap. Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired.

People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.

## Rules of thumb

Regarding the proportion of tap drill to thread major diameter, for standard V threads (ISO V thread and UTS V thread), there are several rules of thumb with strong predictive power:

• A good tap drill is 85% (± 2 pp) of major diameter for coarse threads, and
A good tap drill is 90% (± 2 pp) of major diameter for fine threads.
• For metric V threads, the concept of major minus pitch (i.e., the major or widest diameter of the intended screw in millimeters minus the pitch of the threads of that screw in millimeters per thread) yields a good tap drill diameter.
The major minus pitch technique also works for inch-based threads, but you must first calculate the pitch by converting the fraction of threads-per-inch (TPI) into a decimal. For example, a screw with a pitch of 1/20 in (20 threads per inch) has a pitch of 0.050 in and a ​113 in pitch (13 threads per inch) has a pitch of 0.077 in. Your result will only land near a tap drill size (not directly on one).
• For both of these rules of thumb (85%/90% and major minus pitch), the tap drill size yielded is not necessarily the only possible one, but it is a good one for general use.
• The 85% and 90% rules works best in the range of 14–1 in (6.4–25.4 mm), the sizes most important on many shop floors. Some sizes outside that range have different ratios.

Below, these guidelines are explored with examples.

## Examples

• A good tap drill is 85% (± 2 pp) of major diameter for coarse threads, and
a good tap drill is 90% (± 2 pp) of major diameter for fine threads. [1]
• Example (inch, coarse): For size ​716 (this is the diameter of the intended screw in fraction form)-14 (this is the number of threads per inch; 14 is considered coarse), 0.437 in × 0.85 = 0.371 in. Therefore, a size ​716 screw (​716 ≈ 0.437) with 14 threads per inch (coarse) needs a tap drill with a diameter of about 0.371 inches.
• The drill sizes that are near this are letter U (0.368 in; 84.2%), 9.5 mm (0.374 in; 85.6%), and ​38 in (0.375 in; 85.8%); any of these will work well.
• Example (inch, fine): For ​716-20 (same diameter as the previous example, but this time with 20 threads per inch, which is considered fine), 0.437 in × 0.90 = 0.393 in (i.e., if the threads are to be fine, then a slightly larger diameter drill bit should be used before tapping the hole for the screw).
• The drill sizes that are near this are ​2564 (0.391 in; 89.4%), 10 mm (0.393 in; 90%), and letter X (0.397 in; 90.8%); any of these will work well.
• Example (metric, coarse): For M7.0×1.0 (an intended screw with a diameter of 7.0 mm and a pitch of 1 mm between each thread, which is considered coarse), 7.0 mm × 0.85 = 5.95 mm.
• The drill sizes that are near this are ​1564 in (85%), 6.0 mm (85.7%), and 6.1 mm (87.1%); any of these will work well.
• Example (metric, fine): For M7.0×0.5, 7.0 mm × 0.90 = 6.30.
• The drill sizes that are near this are 6.3 mm (90%), ​14 in (90.7%), 6.4 mm (91.4%), and 6.5 mm (92.9%); any of these will work well.
• For metric V threads, major minus pitch yields a good tap drill diameter.
• Example (metric, coarse): For M7.0 × 1.0, 7.0 − 1.0 = 6.0
• Example (metric, fine): For M7.0 × 0.5, 7.0 − 0.5 = 6.5
• (The 85% coarse, 90% fine guideline, within its effective range, matches this in net effect)
• The major minus pitch also works for inch-based threads, but you must first determine the pitch by looking at the number of treads per inch (TPI; for example, ​120 = 0.050 and ​113 ≈ 0.077), and your result will only land near a tap drill size (not directly on one).
• Example (inch coarse): For ​716-14, 1 in ÷ 14 = 0.071 in; 0.437 in − 0.071 in = 0.366 in;
• The drill sizes that are near this are 9.3 mm (0.366 in) and letter U (0.368 in). In addition, 9.5 mm (0.374 in), and ​38 in (0.375 in) will work well, although major minus pitch by itself does not tell you this; but the 85% ± 2 pp guideline supports it.
• Example (inch fine): For ​716-20, 1 in ÷ 20 = 0.050 in; 0.437 in − 0.050 in = 0.387 in;
• The drill sizes that are near this are letter W (0.386 in) and ​2564 in (0.391 in). In addition, 10 mm (0.393 in), and letter X (0.397 in) will work well, although major minus pitch by itself does not tell you this; but the 90% ± 2 pp guideline supports it.
• For both of these rules of thumb (85%/90% and major minus pitch), the tap drill size yielded is not necessarily the only possible one, but it is a good one for general use.
• Example (metric coarse): For M7.0×1.0, major minus pitch yields 6.0, but 6.1 also works well.
• Example (metric fine): For M7.0×0.5, major minus pitch yields 6.5, which at 92.9% happens to be an example that pushes over the outer bound of the 90% ± 2 pp, but major minus pitch is still valid, although smaller drills (6.3 mm, ​14, 6.4 mm) will work well.

## Chart

Inch-sized drills, increments of ​164 in.
Drills in the number (1–80) and letter (A–Z) series which are specified in decimal inches.
Standard metric drill sizes.
Standard metric drill sizes used for metric taps of the size indicated in the tap size column.
Drill bit diameter Fractional size Drill wire
gauge[2][3]
depth[7][8] (%)
Outer
diameter
(mm, 4 d.p.) (in, 5 d.p.) (in) Close fit[9] Free fit[10]
0.0483 0.00190 107
0.0500 0.00197
0.0584 0.00230 106
0.0686 0.00270 105
0.0787 0.00310 104
0.0889 0.00350 103
0.0991 0.00390 102
0.1000 0.00394
0.1092 0.00430 101
0.1194 0.00470 100
0.1295 0.00510 99
0.1397 0.00550 98
0.1499 0.00590 97
0.1600 0.00630 96
0.1702 0.00670 95
0.1803 0.00710 94
0.1905 0.00750 93
0.2007 0.00790 92
0.2000 0.00787
0.2108 0.00830 91
0.2210 0.00870 90
0.2311 0.00910 89
0.2413 0.00950 88
0.2500 0.00984
0.2540 0.01000 87
0.2667 0.01050 86
0.2794 0.01100 85
0.2921 0.01150 84
0.3000 0.01181
0.3048 0.01200 83
0.3175 0.01250 82
0.3302 0.01300 81
0.3429 0.01350 80
0.3500 0.01378
0.3680 0.01449 79
0.3969 0.01563 164 #0000-160 0.02400 in 0.021 in
0.4000 0.01575
0.4064 0.01600 78
0.4200 0.01654
0.4400 0.01732
0.4500 0.01772
0.4572 0.01800 77
0.4600 0.01811
0.4800 0.01890
0.5000 0.01969
0.5080 0.02000 76
0.5334 0.02100 75
0.5500 0.02165
0.5715 0.02250 74
0.6000 0.02362
0.6096 0.02400 73
0.6350 0.02500 72
0.6500 0.02559
0.6604 0.02600 71 #000-120 0.03700 in
0.7000 0.02756
0.7112 0.02800 70
0.7417 0.02920 69
0.7500 0.02953
0.7874 0.03100 68
0.7938 0.03125 132
0.8000 0.03150
0.8128 0.03200 67
0.8382 0.03300 66
0.8500 0.03346
0.8890 0.03500 65 #00-90 0.05200 in
0.9000 0.03543
0.9144 0.03600 64
0.9398 0.03700 63
0.9500 0.03740
0.9652 0.03800 62
0.9906 0.03900 61
1.0000 0.03937
1.0160 0.04000 60
1.0414 0.04100 59
1.0500 0.04134
1.0668 0.04200 58
1.0922 0.04300 57
1.1000 0.04331
1.1500 0.04528
1.1811 0.04650 56
1.1906 0.04688 364 #0-80 0.06350 in 0.07000 in
1.2000 0.04724
1.2500 0.04921
1.3000 0.05118
1.3208 0.05200 55
1.3500 0.05315
1.3970 0.05500 54
1.4000 0.05512
1.4500 0.05709
1.5000 0.05906
1.5113 0.05950 53 #1-64, #1-72 0.07600 in 0.08100 in
1.5500 0.06102
1.5875 0.06250 116
1.6000 0.06299 M2×0.4 2.2 mm
1.6129 0.06350 52
1.6500 0.06496
1.7000 0.06693
1.7018 0.06700 51 #2-56 0.08900 in 0.09600 in
1.7500 0.06890 M2.2×0.45 2.25 mm
1.7780 0.07000 50 #2-56, #2-64 0.08900 in 0.09600 in
1.8000 0.07087
1.8500 0.07283
1.8542 0.07300 49
1.9000 0.07480
1.9304 0.07600 48
1.9500 0.07677
1.9600 0.07717 #3-48 0.10400 in 0.11000 in 81
1.9700 0.07756 #3-48 0.10400 in 0.11000 in 79
1.9844 0.07813 564 #3-48 0.10400 in 0.11000 in 78
1.9939 0.07850 47 #3-48 0.10400 in 0.11000 in 76
2.0000 0.07874 #3-48 0.10400 in 0.11000 in 75
2.0100 0.07913 #3-48 0.10400 in 0.11000 in 74
2.0200 0.07953 #3-48 0.10400 in 0.11000 in 72
2.0300 0.07992 #3-48 0.10400 in 0.11000 in 71
2.0400 0.08031 #3-48
#3-56
0.10400 in 0.11000 in 69
81
2.0500 0.08071 #3-48
#3-56
M2.5×0.45
0.10400 in

0.11000 in

68
79

2.0574 0.08100 46 #3-48
#3-56
0.10400 in 0.11000 in 66
77
2.0700 0.08150 #3-48
#3-56
0.10400 in 0.11000 in 65
75
2.0828 0.08200 45 #3-48
#3-56
0.10400 in 0.11000 in 66
74
2.0900 0.08228 #3-48
#3-56
0.10400 in 0.11000 in 62
72
2.1000 0.08268 #3-48
#3-56
0.10400 in 0.11000 in 60
70
2.1100 0.08307 #3-48
#3-56
0.10400 in 0.11000 in 59
69
2.1200 0.08346 #3-56 0.10400 in 0.11000 in 67
2.1300 0.08386 #3-56 0.10400 in 0.11000 in 65
2.1400 0.08425 #3-56 0.10400 in 0.11000 in 63
2.1500 0.08465 #3-56
M2.5×0.35
0.10400 in 0.11000 in 62
2.1600 0.08504 #3-56 0.10400 in 0.11000 in 60
2.1700 0.08543 #3-56 0.10400 in 0.11000 in 59
2.1844 0.08600 44 #4-36 0.11600 in 0.12850 in 81
2.1900 0.08622 #4-40 0.11600 in 0.12850 in 81
2.2000 0.08661 #4-40 0.11600 in 0.12850 in 78
2.2100 0.08701 #4-40 0.11600 in 0.12850 in 77
2.2200 0.08740 #4-40 0.11600 in 0.12850 in 76
2.2300 0.08780 #4-40 0.11600 in 0.12850 in 75
2.2400 0.08819 #4-40 0.11600 in 0.12850 in 73
2.2500 0.08858 #4-40 0.11600 in 0.12850 in 72
2.2600 0.08898 #4-40 0.11600 in 0.12850 in 71
2.2606 0.08900 43 #4-40 0.11600 in 0.12850 in 71
2.2700 0.08937 #4-40 0.11600 in 0.12850 in 70
2.2800 0.08976 #4-40 0.11600 in 0.12850 in 68
2.2900 0.09016 #4-40
#4-48
0.11600 in 0.12850 in 67
81
2.3000 0.09055 #4-40
#4-48
0.11600 in 0.12850 in 66
79
2.3100 0.09094 #4-40
#4-48
0.11600 in 0.12850 in 65
78
2.3200 0.09134 #4-40
#4-48
0.11600 in 0.12850 in 64
76
2.3300 0.09173 #4-40
#4-48
0.11600 in 0.12850 in 63
75
2.3400 0.09213 #4-40
#4-48
0.11600 in 0.12850 in 61
74
2.3500 0.09252 #4-40
#4-48
0.11600 in 0.12850 in 60
72
2.3749 0.09350 42 #4-48 0.11600 in 0.12850 in 69
2.3813 0.09375 332
2.4000 0.09449
2.4384 0.09600 41
2.4500 0.09646
2.4892 0.09800 40
2.5000 0.09843 M3×0.5 3.2 mm 75
2.5273 0.09950 39 #5-40 0.12850 in 0.13600 in 78
2.5781 0.10150 38 #5-40 0.12850 in 0.13600 in 72
2.6000 0.10236
2.6416 0.10400 37 #5-44 0.12850 in 0.13600 in 71
2.7000 0.10630
2.7051 0.10650 36 #6-32 0.14400 in 0.14950 in 77 0.14 in
2.7500 0.10827
2.7781 0.10938 764
2.7940 0.11000 35
2.8000 0.11024
2.8194 0.11100 34
2.8702 0.11300 33 #6-40 0.1563 in 0.14 in
2.9000 0.11417 M3.5×0.6
2.9464 0.11600 32
3.0000 0.11811
3.0480 0.12000 31
3.1000 0.12205
3.1750 0.12500 18
3.2000 0.12598
3.2500 0.12795
3.2639 0.12850 30
3.3000 0.12992 M4×0.7 4.10 mm 75
3.4000 0.13386
3.4544 0.13600 29 #8-32 0.16950 in 0.17700 in 69
3.5000 0.13780 M4×0.5 4.10 mm 60
3.5687 0.14050 28
3.5719 0.14063 964
3.6000 0.14173
3.6576 0.14400 27
3.7000 0.14567
3.7338 0.14700 26
3.7500 0.14764
3.7973 0.14950 25 #10-24 0.19600 in 0.20100 in 75
3.8000 0.14961
3.8608 0.15200 24
3.9000 0.15354
3.9116 0.15400 23
3.9688 0.15625 532
3.9878 0.15700 22
4.0000 0.15748
4.0386 0.15900 21 #10-32 0.1960 in 0.2010 in
4.0894 0.16100 20
4.1000 0.16142
4.2000 0.16535 M5×0.8 5.10 mm 75
4.2164 0.16600 19
4.2500 0.16732
4.3053 0.16950 18
4.3656 0.17188 1164
4.3942 0.17300 17
4.4000 0.17323
4.4958 0.17700 16 #12-24 0.22100 in 0.22800 in 72
4.5000 0.17717
4.5720 0.18000 15
4.6000 0.18110
4.6228 0.18200 14
4.6990 0.18500 13
4.7000 0.18504
4.7500 0.18701
4.7625 0.18750 316
4.8000 0.18898
4.8006 0.18900 12
4.8514 0.19100 11
4.9000 0.19291
4.9149 0.19350 10
4.9784 0.19600 9
5.0000 0.19685 M6×1.0 6.10 mm 75
5.0546 0.19900 8
5.1000 0.20079
5.1054 0.20100 7 14-20 0.25700 in 0.26600 in 72
5.1594 0.20313 1364
5.1816 0.20400 6
5.2000 0.20472 M6×0.75 [11] 6.10 mm 60
5.2197 0.20550 5
5.2500 0.20669
5.3000 0.20866
5.3086 0.20900 4
5.4000 0.21260
5.4102 0.21300 3 14-28 0.25700 in 0.26600 in 80
5.5000 0.21654 14-28 0.25700 in 0.26600 in 70
5.5563 0.21875 732 14-28
14-32
(​14-32 UNEF for glow plugs)
0.25700 in 0.26600 in 68
5.6000 0.22047 14-28 0.25700 in 0.26600 in 63
5.6134 0.22100 2 14-28 0.25700 in 0.26600 in 60
5.7000 0.22441
5.7500 0.22638
5.7912 0.22800 1
5.8000 0.22835
5.9000 0.23228
5.9436 0.23400 A
5.9531 0.23438 1564
6.0000 0.23622
6.0452 0.23800 B
6.1000 0.24016 M7×1.0 75
6.1468 0.24200 C
6.2000 0.24409
6.2484 0.24600 D
6.2500 0.24606
6.3000 0.24803
6.3500 0.25000 14
E
6.4000 0.25197
6.5000 0.25591 M7×0.5
6.5278 0.25700 F 516-18 0.32300 in 0.33200 in 77
6.6000 0.25984
6.6294 0.26100 G
6.7000 0.26378
6.7469 0.26563 1764 516-18 74
6.7500 0.26575
6.7564 0.26600 H
6.8000 0.26772
6.9000 0.27165 M8×1.25 75
6.9088 0.27200 I 516-24 0.32300 in 0.33200 in 75
7.0000 0.27559
7.0358 0.27700 J 516-18 50
7.1000 0.27953 M8×1.0 75
7.1374 0.28100 K
7.1438 0.28125 932 516-32
7.2000 0.28346
7.2500 0.28543
7.3000 0.28740
7.3660 0.29000 L
7.4000 0.29134
7.4930 0.29500 M
7.5000 0.29528
7.5406 0.29688 1964
7.6000 0.29921
7.6708 0.30200 N
7.7000 0.30315
7.7500 0.30512
7.8000 0.30709
7.9000 0.31102
7.9375 0.31250 516 38-16 0.38600 in 0.39700 in 77
8.0000 0.31496
8.0264 0.31600 O
8.1000 0.31890
8.2000 0.32283
8.2042 0.32300 P
8.2500 0.32480
8.3000 0.32677
8.3344 0.32813 2164
8.4000 0.33071
8.4328 0.33200 Q 38-24 0.38600 in 0.39700 in 79
8.5000 0.33465 M10×1.5
8.6000 0.33858
8.6106 0.33900 R
8.7000 0.34252
8.7313 0.34375 1132
8.7500 0.34449 M10×1.25
8.8000 0.34646
8.8392 0.34800 S
8.9000 0.35039
9.0000 0.35433 M10×1.0
(spark plug)
9.0932 0.35800 T
9.1000 0.35827
9.1281 0.35938 2364
9.2000 0.36220
9.2500 0.36417
9.3000 0.36614
9.3472 0.36800 U 716-14 0.45310 in 0.46870 in 75
9.4000 0.37008
9.5000 0.37402
9.5250 0.37500 38
9.5758 0.37700 V
9.6000 0.37795
9.7000 0.38189
9.7500 0.38386
9.8000 0.38583
9.8044 0.38600 W
9.9000 0.38976
9.9219 0.39063 2564 716-20 0.45313 in 0.46785 in 72
10.0000 0.39370
10.0838 0.39700 X
10.2616 0.40400 Y
10.3188 0.40625 1332 716-40
10.4902 0.41300 Z
10.5000 0.41339 M12×1.75 75
10.7000 0.42126 M12×1.5 75
10.7156 0.42188 2764 12-13 0.51563 in 0.53125 in 78
10.900 0.42913 M12×1.25
(spark plug)
11.0000 0.43307
11.1125 0.43750 716
11.5000 0.45276
11.5094 0.45313 2964 12-20 0.51563 in 0.53125 in 72
11.9063 0.46875 1532 916-12 0.56250 in 87
12.0000 0.47244
12.2000 0.48031 M14×2 75
12.3031 0.48438 3164 916-12 0.56250 in 68
12.5000 0.49213
12.7000 0.50000 12 916-18 0.56250 in 87
M14×1.5 75
12.8000 0.50393 M14×1.25
(spark plug)
13.0000 0.51181
13.0969 0.51563 3364 916-18 0.56250 in 65
13.4938 0.53125 1732 58-11 0.62500 in 79
13.5000 0.53150
13.8906 0.54688 3564 58-11 0.62500 in 66
14.0000 0.55118
14.2000 0.55906 M16×2 75
14.2875 0.56250 916 58-18 0.62500 in 87
14.5000 0.57087
14.6844 0.57813 3764 58-18 0.62500 in 65
14.7000 0.57874 M16×1.5 75
15.0000 0.59055
15.0813 0.59375 1932
15.4781 0.60938 3964
15.5000 0.61024
15.8750 0.62500 58
16.0000 0.62992
16.2719 0.64063 4164 34-10 84
16.5000 0.64961
16.6688 0.65625 2132 34-10 72
16.8000 0.66141 M18×1.5
(spark plug)
17.0000 0.66929
17.0656 0.67188 4364
17.4625 0.68750 1116 34-16 77
17.5000 0.68898
17.8594 0.70313 4564
18.0000 0.70866
18.2563 0.71875 2332
18.5000 0.72835
18.6531 0.73438 4764
19.0000 0.74803
19.0500 0.75000 34
19.4469 0.76563 4964 78-9 76
19.5000 0.76772
19.8438 0.78125 2532 78-9 65
20.0000 0.78740
20.2406 0.79688 5164 78-14 84
20.5000 0.80709
20.6375 0.81250 1316 78-14 67
21.0000 0.82677
21.0344 0.82813 5364 78-18 NS
(spark plug)
21.4313 0.84375 2732
21.5000 0.84646
21.8281 0.85938 5564 1-8 87
22.0000 0.86614
22.2250 0.87500 78 1-8 77
22.5000 0.88583
22.6219 0.89063 5764 1-8 67
23.0000 0.90551
23.0188 0.90625 2932 1-12 87
23.4156 0.92188 5964 1-12
1-14
72
84
23.5000 0.92520
23.8125 0.93750 1516 1-14 67
24.0000 0.94488
24.2094 0.95313 6164
24.5000 0.96457
24.6063 0.96875 3132 1 18-7 84
25.0000 0.98425
25.0031 0.98438 6364 1 18-7 76
25.4000 1.00000 1 1 18-7 67
25.5000 1.00394
25.7969 1.01563 1 164
26.0000 1.02362
26.1938 1.03125 1 132 1 18-12 87
26.5000 1.04331
26.5906 1.04688 1 364 1 18-12 72
26.9875 1.06250 1 116
27.0000 1.06299
27.5000 1.08268
28.0000 1.10236
28.1781 1.10938 1 764 1 14-7 76
28.5000 1.12205
28.5750 1.12500 1 18 1 14-7 67
29.0000 1.14173
29.3688 1.15625 1 532 1 14-12 87
29.5000 1.16142
29.7656 1.17188 1 1164 1 14-12 72
30.0000 1.18110
30.1625 1.18750 1 316 1 38-6 87
30.5000 1.20079
30.5594 1.20313 1 1364 1 38-6 79
30.9563 1.21875 1 732 1 38-6 72
31.0000 1.22047
31.3531 1.23438 1 1564 1 38-6 65
31.5000 1.24016
32.0000 1.25984
32.5000 1.27953
32.5438 1.28125 1 932 1 38-12 87
32.9406 1.29688 1 1964 1 38-12 72
33.0000 1.29921
33.3375 1.31250 1 516 1 12-6 87
33.5000 1.31890
33.7344 1.32813 1 2164 1 12-6 79
34.0000 1.33858
34.1313 1.34375 1 1132 1 12-6 72
34.5000 1.35827
34.5281 1.35938 1 2364 1 12-6 65
35.0000 1.37795
35.5000 1.39764
35.7188 1.40625 1 1332 1 12-12 87
36.0000 1.41732
36.1156 1.42188 1 2764 1 12-12 72
36.5000 1.43701

If theoretical thread percentage not given, assume 75% ± 10%
Theoretical percentage of thread should not be relied upon for threads of included angles other than 60 degrees.

## References

1. ^ "Drill Bit Size Charts and Rule of Thumb".
2. ^ "Continuous Drill Bit Sizes". Archived from the original on 2006-07-19. Retrieved 2006-08-29.
3. ^ "Decimal Equivalents". Ohio State University. Archived from the original on 2006-09-02. Retrieved 2006-08-29. External link in `|work=` (help)
4. ^ "Tap Drill Sizes and Calculator". newmantools.com. Retrieved 2006-08-04. External link in `|work=` (help)
5. ^ "Tap Drill Sizes for Universal and M-Profile Screw Threads". precisiontwistdrill.com. Retrieved 2006-08-04. External link in `|work=` (help)
6. ^ "NC, NF, NEF to one inch in diameter". Sizes.com. Archived from the original on 2006-09-29. Retrieved 2006-09-01. External link in `|work=` (help)
7. ^ "High performance taps" (PDF). guhring.com. Retrieved 2010-10-07. External link in `|publisher=` (help)
8. ^ "Tap Drill Sizes". widell.com. Archived from the original on 2006-11-14. Retrieved 2006-09-01. External link in `|work=` (help)
9. ^ "Tap & Clearance Drills For Common Screws". Small Parts Inc. Retrieved 2010-10-07. External link in `|work=` (help)
10. ^ "Tap Drill Sizes". efunda.com. Retrieved 2006-08-04. External link in `|work=` (help)
11. ^ http://www.littlemachineshop.com/reference/tapdrillsizes.pdf