# List of drill and tap sizes

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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 (20 threads per inch) has a pitch of .050 and a 1/13 pitch (13 threads per inch) has a pitch of .077. 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%/90% rule works best in the range of 1/4"-1" (6 to 25 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.
• Example (inch, coarse): For size 7/16 (this is the diameter of the intended screw in fraction form)-14 (this is the number of threads per inch— "14" is considered "coarse"), .437" × .85 = .371". Therefore a size 7/16 screw (7/16=.437) with 14 threads per inch (coarse) needs a tap drill with a diameter of about .371 inches.
• The drill sizes that are near this are letter U (.368"; 84.2%), 9.5 mm (.374; 85.6%), and 3/8" (.375; 85.8%); any of these will work well.
• Example (inch, fine): For 7/16-20 (same diameter as the previous example, but this time with 20 threads per inch, which is considered "fine"), .437" × .90 = .393" (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 25/64" (.391"; 89.4%), 10 mm (.393"; 90%), and letter X (.397"; 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 × .85 = 5.95.
• The drill sizes that are near this are 15/64" (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 × .90 = 6.30.
• The drill sizes that are near this are 6.3 mm (90%), 1/4" (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%:90%::C:F 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, 1/20 = .050 and 1/13 = .077), and your result will only land near a tap drill size (not directly on one).
• Example (inch coarse): For 7/16-14, 1" ÷ 14 = .071"; .437" − .071" = .366";
• The drill sizes that are near this are 9.3 mm (.366") and letter U (.368"). In addition, 9.5 mm (.374), and 3/8" (.375) 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 7/16-20, 1" ÷ 20 = .050"; .437" − .050" = .387";
• The drill sizes that are near this are letter W (.386") and 25/64" (.391"). In addition, 10 mm (.393"), and letter X (.397") 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, 1/4", 6.4 mm) will work well.

## Chart

Inch-sized drills, increments of 1/64".
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 Drill bit diameter Fractional size (inches) Drill wire
gauge[1][2]
Tap size[3][4][5] Clearance Clearance Theoretical percentage of thread[6][7] Outer diameter
[mm (4 d.p.)] [in (5 d.p.)] [in] [close fit][8] [free fit][9] [%]
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 1/64 #0000-160 0.02400" 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"
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 1/32
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"
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 3/64 #0-80 0.06350" 0.07000"
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" 0.08100"
1.5500 0.06102
1.5875 0.06250 1/16
1.6000 0.06299 M2x0.4 2.2mm
1.6129 0.06350 52
1.6500 0.06496
1.7000 0.06693
1.7018 0.06700 51 #2-56 0.08900" 0.09600"
1.7500 0.06890 M2.2x0.45 2.25mm
1.7780 0.07000 50 #2-56, #2-64 0.08900" 0.09600"
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" 0.11000" 81
1.9700 0.07756 #3-48 0.10400" 0.11000" 79
1.9844 0.07813 5/64 #3-48 0.10400" 0.11000" 78
1.9939 0.07850 47 #3-48 0.10400" 0.11000" 76
2.0000 0.07874 #3-48 0.10400" 0.11000" 75
2.0100 0.07913 #3-48 0.10400" 0.11000" 74
2.0200 0.07953 #3-48 0.10400" 0.11000" 72
2.0300 0.07992 #3-48 0.10400" 0.11000" 71
2.0400 0.08031 #3-48
#3-56
0.10400" 0.11000" 69
81
2.0500 0.08071 #3-48
#3-56
M2.5x0.45
0.10400"

0.11000"

68
79

2.0574 0.08100 46 #3-48
#3-56
0.10400" 0.11000" 66
77
2.0700 0.08150 #3-48
#3-56
0.10400" 0.11000" 65
75
2.0828 0.08200 45 #3-48
#3-56
0.10400" 0.11000" 66
74
2.0900 0.08228 #3-48
#3-56
0.10400" 0.11000" 62
72
2.1000 0.08268 #3-48
#3-56
M2.5x0.35
0.10400" 0.11000" 60
70
2.1100 0.08307 #3-48
#3-56
0.10400" 0.11000" 59
69
2.1200 0.08346 #3-56 0.10400" 0.11000" 67
2.1300 0.08386 #3-56 0.10400" 0.11000" 65
2.1400 0.08425 #3-56 0.10400" 0.11000" 63
2.1500 0.08465 #3-56 0.10400" 0.11000" 62
2.1600 0.08504 #3-56 0.10400" 0.11000" 60
2.1700 0.08543 #3-56 0.10400" 0.11000" 59
2.1844 0.08600 44 #4-36 0.11600" 0.12850" 81
2.1900 0.08622 #4-40 0.11600" 0.12850" 81
2.2000 0.08661 #4-40 0.11600" 0.12850" 78
2.2100 0.08701 #4-40 0.11600" 0.12850" 77
2.2200 0.08740 #4-40 0.11600" 0.12850" 76
2.2300 0.08780 #4-40 0.11600" 0.12850" 75
2.2400 0.08819 #4-40 0.11600" 0.12850" 73
2.2500 0.08858 #4-40 0.11600" 0.12850" 72
2.2600 0.08898 #4-40 0.11600" 0.12850" 71
2.2606 0.08900 43 #4-40 0.11600" 0.12850" 71
2.2700 0.08937 #4-40 0.11600" 0.12850" 70
2.2800 0.08976 #4-40 0.11600" 0.12850" 68
2.2900 0.09016 #4-40
#4-48
0.11600" 0.12850" 67
81
2.3000 0.09055 #4-40
#4-48
0.11600" 0.12850" 66
79
2.3100 0.09094 #4-40
#4-48
0.11600" 0.12850" 65
78
2.3200 0.09134 #4-40
#4-48
0.11600" 0.12850" 64
76
2.3300 0.09173 #4-40
#4-48
0.11600" 0.12850" 63
75
2.3400 0.09213 #4-40
#4-48
0.11600" 0.12850" 61
74
2.3500 0.09252 #4-40
#4-48
0.11600" 0.12850" 60
72
2.3749 0.09350 42 #4-48 0.11600" 0.12850" 69
2.3813 0.09375 3/32
2.4000 0.09449
2.4384 0.09600 41
2.4500 0.09646
2.4892 0.09800 40
2.5000 0.09843 M3x0.5 3.2mm 75
2.5273 0.09950 39 #5-40 0.12850" 0.13600" 78
2.5781 0.10150 38 #5-40 0.12850" 0.13600" 72
2.6000 0.10236
2.6416 0.10400 37 #5-44 0.12850" 0.13600" 71
2.7000 0.10630
2.7051 0.10650 36 #6-32 0.14400" 0.14950" 77 .14
2.7500 0.10827
2.7781 0.10938 7/64
2.7940 0.11000 35
2.8000 0.11024
2.8194 0.11100 34
2.8702 0.11300 33 #6-40 .1563 .14
2.9000 0.11417 M3.5x0.6
2.9464 0.11600 32
3.0000 0.11811
3.0480 0.12000 31
3.1000 0.12205
3.1750 0.12500 1/8
3.2000 0.12598
3.2500 0.12795
3.2639 0.12850 30
3.3000 0.12992 M4x0.7 4.10mm 75
3.4000 0.13386
3.4544 0.13600 29 #8-32 0.16950" 0.17700" 69
3.5000 0.13780 M4x0.7 4.10mm 60
3.5687 0.14050 28
3.5719 0.14063 9/64
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" 0.20100" 75
3.8000 0.14961
3.8608 0.15200 24
3.9000 0.15354
3.9116 0.15400 23
3.9688 0.15625 5/32
3.9878 0.15700 22
4.0000 0.15748
4.0386 0.15900 21 #10-32 0.1960" 0.2010"
4.0894 0.16100 20
4.1000 0.16142
4.2000 0.16535 M5x0.8 5.10mm 75
4.2164 0.16600 19
4.2500 0.16732
4.3053 0.16950 18
4.3656 0.17188 11/64
4.3942 0.17300 17
4.4000 0.17323
4.4958 0.17700 16 #12-24 0.22100" 0.22800" 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 3/16
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 M6x1.0 6.10mm 75
5.0546 0.19900 8
5.1000 0.20079
5.1054 0.20100 7 1/4-20 0.25700" 0.26600" 72
5.1594 0.20313 13/64
5.1816 0.20400 6
5.2000 0.20472 M6x1.0 6.10mm 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 1/4-28 0.25700" 0.26600" 80
5.5000 0.21654 1/4-28 0.25700" 0.26600" 70
5.5563 0.21875 7/32 1/4-28 0.25700" 0.26600" 68
5.6000 0.22047 1/4-28 0.25700" 0.26600" 63
5.6134 0.22100 2 1/4-28 0.25700" 0.26600" 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 15/64
6.0000 0.23622
6.0452 0.23800 B
6.1000 0.24016 M7x1.0 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 1/4
E
6.4000 0.25197
6.5000 0.25591 M7X0.5
6.5278 0.25700 F 5/16-18 0.32300" 0.33200" 77
6.6000 0.25984
6.6294 0.26100 G
6.7000 0.26378
6.7469 0.26563 17/64
6.7500 0.26575
6.7564 0.26600 H
6.8000 0.26772
6.9000 0.27165 M8x1.25 75
6.9088 0.27200 I 5/16-24 0.32300" 0.33200" 75
7.0000 0.27559
7.0358 0.27700 J
7.1000 0.27953 M8x1.0 75
7.1374 0.28100 K
7.1438 0.28125 9/32 5/16-32
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 19/64
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 5/16 3/8-16 0.38600" 0.39700" 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 21/64
8.4000 0.33071
8.4328 0.33200 Q 3/8-24 0.38600" 0.39700" 79
8.5000 0.33465
8.6000 0.33858
8.6106 0.33900 R
8.7000 0.34252 M10x1.5 75
8.7313 0.34375 11/32
8.7500 0.34449
8.8000 0.34646
8.8392 0.34800 S
8.9000 0.35039 M10x1.25 75
9.0000 0.35433
9.0932 0.35800 T
9.1000 0.35827 M10x1.0
(spark plug)
75
9.1281 0.35938 23/64
9.2000 0.36220
9.2500 0.36417
9.3000 0.36614
9.3472 0.36800 U 7/16-14 0.45310" 0.46870" 75
9.4000 0.37008
9.5000 0.37402
9.5250 0.37500 3/8
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 25/64 7/16-20 0.45313" 0.46785" 72
10.0000 0.39370
10.0838 0.39700 X
10.2616 0.40400 Y
10.3188 0.40625 13/32 7/16 - 40
10.4902 0.41300 Z
10.5000 0.41339 M12x1.75 75
10.7000 0.42126 M12x1.5 75
10.7156 0.42188 27/64 1/2-13 0.51563" 0.53125" 78
10.900 0.42913 M12X1.25
(spark plug)
11.0000 0.43307
11.1125 0.43750 7/16
11.5000 0.45276
11.5094 0.45313 29/64 1/2-20 0.51563" 0.53125" 72
11.9063 0.46875 15/32 9/16-12 0.56250" 87
12.0000 0.47244
12.2000 0.48031 M14x2 75
12.3031 0.48438 31/64 9/16-12 0.56250" 68
12.5000 0.49213
12.7000 0.50000 1/2 9/16-18 0.56250" 87
M14x1.5 75
12.8000 0.50393 M14x1.25
(spark plug)
13.0000 0.51181
13.0969 0.51563 33/64 9/16-18 0.56250" 65
13.4938 0.53125 17/32 5/8-11 0.62500" 79
13.5000 0.53150
13.8906 0.54688 35/64 5/8-11 0.62500" 66
14.0000 0.55118
14.2000 0.55906 M16x2 75
14.2875 0.56250 9/16 5/8-18 0.62500" 87
14.5000 0.57087
14.6844 0.57813 37/64 5/8-18 0.62500" 65
14.7000 0.57874 M16x1.5 75
15.0000 0.59055
15.0813 0.59375 19/32
15.4781 0.60938 39/64
15.5000 0.61024
15.8750 0.62500 5/8
16.0000 0.62992
16.2719 0.64063 41/64 3/4-10 84
16.5000 0.64961
16.6688 0.65625 21/32 3/4-10 72
16.8000 0.66141 M18x1.5
(spark plug)
17.0000 0.66929
17.0656 0.67188 43/64
17.4625 0.68750 11/16 3/4-16 77
17.5000 0.68898
17.8594 0.70313 45/64
18.0000 0.70866
18.2563 0.71875 23/32
18.5000 0.72835
18.6531 0.73438 47/64
19.0000 0.74803
19.0500 0.75000 3/4
19.4469 0.76563 49/64 7/8-9 76
19.5000 0.76772
19.8438 0.78125 25/32 7/8-9 65
20.0000 0.78740
20.2406 0.79688 51/64 7/8-14 84
20.5000 0.80709
20.6375 0.81250 13/16 7/8-14 67
21.0000 0.82677
21.0344 0.82813 53/64 7/8-18 NS
(spark plug)
21.4313 0.84375 27/32
21.5000 0.84646
21.8281 0.85938 55/64 1-8 87
22.0000 0.86614
22.2250 0.87500 7/8 1-8 77
22.5000 0.88583
22.6219 0.89063 57/64 1-8 67
23.0000 0.90551
23.0188 0.90625 29/32 1-12 87
23.4156 0.92188 59/64 1-12
1-14
72
84
23.5000 0.92520
23.8125 0.93750 15/16 1-14 67
24.0000 0.94488
24.2094 0.95313 61/64
24.5000 0.96457
24.6063 0.96875 31/32 1 1/8-7 84
25.0000 0.98425
25.0031 0.98438 63/64 1 1/8-7 76
25.4000 1.00000 1 1 1/8-7 67
25.5000 1.00394
25.7969 1.01563 1 1/64
26.0000 1.02362
26.1938 1.03125 1 1/32 1 1/8-12 87
26.5000 1.04331
26.5906 1.04688 1 3/64 1 1/8-12 72
26.9875 1.06250 1 1/16
27.0000 1.06299
27.5000 1.08268
28.0000 1.10236
28.1781 1.10938 1 7/64 1 1/4-7 76
28.5000 1.12205
28.5750 1.12500 1 1/8 1 1/4-7 67
29.0000 1.14173
29.3688 1.15625 1 5/32 1 1/4-12 87
29.5000 1.16142
29.7656 1.17188 1 11/64 1 1/4-12 72
30.0000 1.18110
30.1625 1.18750 1 3/16 1 3/8-6 87
30.5000 1.20079
30.5594 1.20313 1 13/64 1 3/8-6 79
30.9563 1.21875 1 7/32 1 3/8-6 72
31.0000 1.22047
31.3531 1.23438 1 15/64 1 3/8-6 65
31.5000 1.24016
32.0000 1.25984
32.5000 1.27953
32.5438 1.28125 1 9/32 1 3/8-12 87
32.9406 1.29688 1 19/64 1 3/8-12 72
33.0000 1.29921
33.3375 1.31250 1 5/16 1 1/2-6 87
33.5000 1.31890
33.7344 1.32813 1 21/64 1 1/2-6 79
34.0000 1.33858
34.1313 1.34375 1 11/32 1 1/2-6 72
34.5000 1.35827
34.5281 1.35938 1 23/64 1 1/2-6 65
35.0000 1.37795
35.5000 1.39764
35.7188 1.40625 1 13/32 1 1/2-12 87
36.0000 1.41732
36.1156 1.42188 1 27/64 1 1/2-12 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.
See http://www.newmantools.com/taps/micro.htm for more information.

## References

1. ^ "Continuous Drill Bit Sizes". Archived from the original on 2006-07-19. Retrieved 2006-08-29.
2. ^ "Decimal Equivalents". Ohio State University. Archived from the original on 2006-09-02. Retrieved 2006-08-29.
3. ^ "Tap Drill Sizes and Calculator". newmantools.com. Retrieved 2006-08-04.
4. ^ "Tap Drill Sizes for Universal and M-Profile Screw Threads". precisiontwistdrill.com. Retrieved 2006-08-04.
5. ^ "NC, NF, NEF to one inch in diameter". Sizes.com. Retrieved 2006-09-01.
6. ^ "High performance taps" (PDF). guhring.com. Retrieved 2010-10-07.
7. ^ "Tap Drill Sizes". widell.com. Retrieved 2006-09-01.
8. ^ "Tap & Clearance Drills For Common Screws". Small Parts Inc. Archived from the original on 2007-10-08. Retrieved 2010-10-07.
9. ^ "Tap Drill Sizes". efunda.com. Retrieved 2006-08-04.