Tag: Drill

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National Pipe Thread (NPT) Tap Drill Size

Below is the National Pipe Thread – NPT Tap Drill Size Chart.  It tells us what size hole must be drilled to begin tapping the tapered NPT thread.

Standard NPT Tap Drill Sizes
NPT Size
 Tap Drill Size (in.)
Decimal Equivalent (in.)
1/16 – 27
“C”
0.242
1/8 – 27
“Q”
0.332
1/4 – 18
7/16
0.438
3/8 – 18
9/16
0.562
1/2 – 14
45/64
0.703
3/4 – 14
29/32
0.906
1.0 – 11•1/2
1•9/64
1.141
1•1/4 – 11•1/2
1•31/64
1.484
1•1/2 – 11•1/2
1•23/32
1.719
2.0 – 11•1/2
2•3/16
2.188
2•1/2 – 8
2•39/64
2.609
3.0 – 8
3•15/64
3.234

Metric Tap Drill Sizes
Standard UNC Tap Drill Sizes
Standard UNF Tap Drill Sizes

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Drill Size Chart – Standard Fractional, Letter, Gauge and Metric

Why do you need a Drill Size Chart?  Because what the hell is the diameter of a size “F” drill bit?

Drill size Diameter (in) Diameter (mm)
#107 0.0019 0.0483
0.05 mm 0.0020 0.0500
#106 0.0023 0.0584
#105 0.0027 0.0686
#104 0.0031 0.0787
#103 0.0035 0.0889
#102 0.0039 0.0991
0.1 mm 0.0039 0.1000
#101 0.0043 0.1092
#100 0.0047 0.1194
#99 0.0051 0.1295
#98 0.0055 0.1397
#97 0.0059 0.1499
#96 0.0063 0.1600
#95 0.0067 0.1702
#94 0.0071 0.1803
#93 0.0075 0.1905
0.2 mm 0.0079 0.2000
#92 0.0079 0.2007
#91 0.0083 0.2108
#90 0.0087 0.2210
#89 0.0091 0.2311
#88 0.0095 0.2413
#87 0.0100 0.2540
#86 0.0105 0.2667
#85 0.0110 0.2794
#84 0.0115 0.2921
0.3 mm 0.0118 0.3000
#83 0.0120 0.3048
#82 0.0125 0.3175
#81 0.0130 0.3302
#80 0.0135 0.3429
#79 0.0145 0.3680
1/64 in 0.0156 0.3969
0.4 mm 0.0158 0.4000
#78 0.0160 0.4064
#77 0.0180 0.4572
0.5 mm 0.0197 0.5000
#76 0.0200 0.5080
#75 0.0210 0.5334
#74 0.0225 0.5715
0.6 mm 0.0236 0.6000
#73 0.0240 0.6096
#72 0.0250 0.6350
#71 0.0260 0.6604
0.7 mm 0.0276 0.7000
#70 0.0280 0.7112
#69 0.0292 0.7417
#68 0.0310 0.7874
1/32 in 0.0313 0.7938
0.8 mm 0.0315 0.8000
#67 0.0320 0.8128
#66 0.0330 0.8382
#65 0.0350 0.8890
0.9 mm 0.0354 0.9000
#64 0.0360 0.9144
#63 0.0370 0.9398
#62 0.0380 0.9652
#61 0.0390 0.9906
1 mm 0.0394 1.0000
#60 0.0400 1.0160
#59 0.0410 1.0414
#58 0.0420 1.0668
#57 0.0430 1.0922
1.1 mm 0.0433 1.1000
#56 0.0465 1.1811
3/64 in 0.0469 1.1906
1.2 mm 0.0472 1.2000
1.3 mm 0.0512 1.3000
#55 0.0520 1.3208
#54 0.0550 1.3970
1.4 mm 0.0551 1.4000
1.5 mm 0.0591 1.5000
#53 0.0595 1.5113
1/16 in 0.0625 1.5875
1.6 mm 0.0630 1.6000
#52 0.0635 1.6129
1.7 mm 0.0669 1.7000
#51 0.0670 1.7018
#50 0.0700 1.7780
1.8 mm 0.0709 1.8000
#49 0.0730 1.8542
1.9 mm 0.0748 1.9000
#48 0.0760 1.9304
5/64 in 0.0781 1.9844
#47 0.0785 1.9939
2 mm 0.0787 2.0000
#46 0.0810 2.0574
#45 0.0820 2.0828
2.1 mm 0.0827 2.1000
#44 0.0860 2.1844
2.2 mm 0.0866 2.2000
#43 0.0890 2.2606
2.3 mm 0.0906 2.3000
#42 0.0935 2.3749
3/32 in 0.0938 2.3813
2.4 mm 0.0945 2.4000
#41 0.0960 2.4384
#40 0.0980 2.4892
2.5 mm 0.0984 2.5000
#39 0.0995 2.5273
#38 0.1015 2.5781
2.6 mm 0.1024 2.6000
#37 0.1040 2.6416
2.7 mm 0.1063 2.7000
#36 0.1065 2.7051
7/64 in 0.1094 2.7781
#35 0.1100 2.7940
2.8 mm 0.1102 2.8000
#34 0.1110 2.8194
#33 0.1130 2.8702
2.9 mm 0.1142 2.9000
#32 0.1160 2.9464
3 mm 0.1181 3.0000
#31 0.1200 3.0480
3.1 mm 0.1221 3.1000
1/8 in 0.1250 3.1750
3.2 mm 0.1260 3.2000
#30 0.1285 3.2639
3.3 mm 0.1299 3.3000
3.4 mm 0.1339 3.4000
#29 0.1360 3.4544
3.5 mm 0.1378 3.5000
#28 0.1405 3.5687
9/64 in 0.1406 3.5719
3.6 mm 0.1417 3.6000
#27 0.1440 3.6576
3.7 mm 0.1457 3.7000
#26 0.1470 3.7338
#25 0.1495 3.7973
3.8 mm 0.1496 3.8000
#24 0.1520 3.8608
3.9 mm 0.1535 3.9000
#23 0.1540 3.9116
5/32 in 0.1563 3.9688
#22 0.1570 3.9878
4 mm 0.1575 4.0000
#21 0.1590 4.0386
#20 0.1610 4.0894
4.1 mm 0.1614 4.1000
4.2 mm 0.1654 4.2000
#19 0.1660 4.2164
4.3 mm 0.1693 4.3000
#18 0.1695 4.3053
11/64 in 0.1719 4.3656
#17 0.1730 4.3942
4.4 mm 0.1732 4.4000
#16 0.1770 4.4958
4.5 mm 0.1772 4.5000
#15 0.1800 4.5720
4.6 mm 0.1811 4.6000
#14 0.1820 4.6228
#13 0.1850 4.6990
4.7 mm 0.1850 4.7000
3/16 in 0.1875 4.7625
4.8 mm 0.1890 4.8000
#12 0.1890 4.8006
#11 0.1910 4.8514
4.9 mm 0.1929 4.9000
#10 0.1935 4.9149
#9 0.1960 4.9784
5 mm 0.1969 5.0000
#8 0.1990 5.0546
5.1 mm 0.2008 5.1000
#7 0.2010 5.1054
13/64 in 0.2031 5.1594
#6 0.2040 5.1816
5.2 mm 0.2047 5.2000
#5 0.2055 5.2197
5.3 mm 0.2087 5.3000
#4 0.2090 5.3086
5.4 mm 0.2126 5.4000
#3 0.2130 5.4102
5.5 mm 0.2165 5.5000
7/32 in 0.2188 5.5563
5.6 mm 0.2205 5.6000
#2 0.2210 5.6134
5.7 mm 0.2244 5.7000
#1 0.2280 5.7912
5.8 mm 0.2284 5.8000
5.9 mm 0.2323 5.9000
A 0.2340 5.9436
15/64 in 0.2344 5.9531
6 mm 0.2362 6.0000
B 0.2380 6.0452
6.1 mm 0.2402 6.1000
C 0.2420 6.1468
6.2 mm 0.2441 6.2000
D 0.2460 6.2484
6.3 mm 0.2480 6.3000
1/4 in 0.2500 6.3500
E 0.2500 6.3500
6.4 mm 0.2520 6.4000
6.5 mm 0.2559 6.5000
F 0.2570 6.5278
6.6 mm 0.2598 6.6000
G 0.2610 6.6294
6.7 mm 0.2638 6.7000
17/64 in 0.2656 6.7469
H 0.2660 6.7564
6.8 mm 0.2677 6.8000
6.9 mm 0.2717 6.9000
I 0.2720 6.9088
7 mm 0.2756 7.0000
J 0.2770 7.0358
7.1 mm 0.2795 7.1000
K 0.2810 7.1374
9/32 in 0.2813 7.1438
7.2 mm 0.2835 7.2000
7.3 mm 0.2874 7.3000
L 0.2900 7.3660
7.4 mm 0.2913 7.4000
M 0.2950 7.4930
7.5 mm 0.2953 7.5000
19/64 in 0.2969 7.5406
7.6 mm 0.2992 7.6000
N 0.3020 7.6708
7.7 mm 0.3032 7.7000
7.8 mm 0.3071 7.8000
7.9 mm 0.3110 7.9000
5/16 in 0.3125 7.9375
8 mm 0.3150 8.0000
O 0.3160 8.0264
8.1 mm 0.3189 8.1000
8.2 mm 0.3228 8.2000
P 0.3230 8.2042
8.3 mm 0.3268 8.3000
21/64 in 0.3281 8.3344
8.4 mm 0.3307 8.4000
Q 0.3320 8.4328
8.5 mm 0.3347 8.5000
8.6 mm 0.3386 8.6000
R 0.3390 8.6106
8.7 mm 0.3425 8.7000
11/32 in 0.3438 8.7313
8.8 mm 0.3465 8.8000
S 0.3480 8.8392
8.9 mm 0.3504 8.9000
9 mm 0.3543 9.0000
T 0.3580 9.0932
9.1 mm 0.3583 9.1000
23/64 in 0.3594 9.1281
9.2 mm 0.3622 9.2000
9.3 mm 0.3661 9.3000
U 0.3680 9.3472
9.4 mm 0.3701 9.4000
9.5 mm 0.3740 9.5000
3/8 in 0.3750 9.5250
V 0.3770 9.5758
9.6 mm 0.3780 9.6000
9.7 mm 0.3819 9.7000
9.8 mm 0.3858 9.8000
W 0.3860 9.8044
9.9 mm 0.3898 9.9000
25/64 in 0.3906 9.9219
10 mm 0.3937 10.0000
X 0.3970 10.0838
Y 0.4040 10.2616
13/32 in 0.4063 10.3188
Z 0.4130 10.4902
10.5 mm 0.4134 10.5000
27/64 in 0.4219 10.7156
11 mm 0.4331 11.0000
7/16 in 0.4375 11.1125
11.5 mm 0.4528 11.5000
29/64 in 0.4531 11.5094
15/32 in 0.4688 11.9063
12 mm 0.4724 12.0000
31/64 in 0.4844 12.3031
12.5 mm 0.4921 12.5000
1/2 in 0.5000 12.7000
13 mm 0.5118 13.0000
33/64 in 0.5156 13.0969
17/32 in 0.5313 13.4938
13.5 mm 0.5315 13.5000
35/64 in 0.5469 13.8906
14 mm 0.5512 14.0000
9/16 in 0.5625 14.2875
14.5 mm 0.5709 14.5000
37/64 in 0.5781 14.6844
15 mm 0.5906 15.0000
19/32 in 0.5938 15.0813
39/64 in 0.6094 15.4781
15.5 mm 0.6102 15.5000
5/8 in 0.6250 15.8750
16 mm 0.6299 16.0000
41/64 in 0.6406 16.2719
16.5 mm 0.6496 16.5000
17 mm 0.6693 17.0000
43/64 in 0.6719 17.0656
11/16 in 0.6875 17.4625
17.5 mm 0.6890 17.5000
45/64 in 0.7031 17.8594
18 mm 0.7087 18.0000
23/32 in 0.7188 18.2563
18.5 mm 0.7284 18.5000
47/64 in 0.7344 18.6531
19 mm 0.7480 19.0000
3/4 in 0.7500 19.0500
49/64 in 0.7656 19.4469
19.5 mm 0.7677 19.5000
25/32 in 0.7813 19.8438
20 mm 0.7874 20.0000
51/64 in 0.7969 20.2406
20.5 mm 0.8071 20.5000
13/16 in 0.8125 20.6375
21 mm 0.8268 21.0000
53/64 in 0.8281 21.0344
27/32 in 0.8438 21.4313
21.5 mm 0.8465 21.5000
55/64 in 0.8594 21.8281
22 mm 0.8661 22.0000
7/8 in 0.8750 22.2250
22.5 mm 0.8858 22.5000
57/64 in 0.8906 22.6219
23 mm 0.9055 23.0000
29/32 in 0.9063 23.0188
21/23 in 0.9130 23.1913
59/64 in 0.9219 23.4156
23.5 mm 0.9252 23.5000
15/16 in 0.9375 23.8125
24 mm 0.9449 24.0000
61/64 in 0.9531 24.2094
24.5 mm 0.9646 24.5000
31/32 in 0.9688 24.6063
25 mm 0.9843 25.0000
63/64 in 0.9844 25.0031
1 in 1.0000 25.4000
25.5 mm 1.0039 25.5000
1 1/64 in 1.0156 25.7969
26 mm 1.0236 26.0000
1 1/32 in 1.0313 26.1938
26.5 mm 1.0433 26.5000
1 3/64 in 1.0469 26.5906
1 1/16 in 1.0625 26.9875
27 mm 1.0630 27.0000
1 5/64 in 1.0781 27.3844
27.5 mm 1.0827 27.5000
1 3/32 in 1.0938 27.7813
28 mm 1.1024 28.0000
1 7/64 in 1.1094 28.1781
28.5 mm 1.1221 28.5000
1 1/8 in 1.1250 28.5750
1 9/64 in 1.1406 28.9719
29 mm 1.1417 29.0000
1 5/32 in 1.1563 29.3688
29.5 mm 1.1614 29.5000
1 11/64 in 1.1719 29.7656
30 mm 1.1811 30.0000
1 3/16 in 1.1875 30.1625
30.5 mm 1.2008 30.5000
1 13/64 in 1.2031 30.5594
1 7/32 in 1.2188 30.9563
31 mm 1.2205 31.0000
1 15/64 in 1.2344 31.3531
31.5 mm 1.2402 31.5000
1 1/4 in 1.2500 31.7500
32 mm 1.2598 32.0000
1 17/64 in 1.2656 32.1469
32.5 mm 1.2795 32.5000
1 9/32 in 1.2813 32.5438
1 19/64 in 1.2969 32.9406
33 mm 1.2992 33.0000
1 5/16 in 1.3125 33.3375
33.5 mm 1.3189 33.5000
1 21/64 in 1.3281 33.7344
34 mm 1.3386 34.0000
1 11/32 in 1.3438 34.1313
34.5 mm 1.3583 34.5000
1 23/64 in 1.3594 34.5281
1 3/8 in 1.3750 34.9250
35 mm 1.3780 35.0000
1 25/64 in 1.3906 35.3219
35.5 mm 1.3976 35.5000
1 13/32 in 1.4063 35.7188
36 mm 1.4173 36.0000
1 27/64 in 1.4219 36.1156
36.5 mm 1.4370 36.5000
1 7/16 in 1.4375 36.5125
1 29/64 in 1.4531 36.9094
37 mm 1.4567 37.0000
1 15/32 in 1.4688 37.3063
37.5 mm 1.4764 37.5000
1 31/64 in 1.4844 37.7031
38 mm 1.4961 38.0000
1 1/2 in 1.5000 38.1000

The Drill Size Chart is necessary because imperial sizing, much like the English language, if full of bastard sizing and nomenclature.

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Metric Thread – Tap Drill / Clearance Drill

Below is a table for metric tap drill sizes.  It covers both threaded holes (when you are cutting thread) and clearance holes (when you are simply placing a bolt through a hole).


Metric Tap Drill Chart
Tap size Major
Dia (mm)		 Threads
per 		Tap Drill
(mm)		 Tap Drill
(inch)		 Clearance Hole
(mm)		 Clearance Hole
(inch)
M1.6×0.35 1.6 0.35 1.25 #55 1.8 #49
M2x0.4 2.0 0.40 1.60 #52 2.4 #41
M2.5×0.45 2.5 0.45 2.05 #46 2.9 #32
M3x.05 3.0 0.50 2.50 #39 3.4 #29
M3.5×0.6 3.5 0.60 2.90 #32 3.9 #23
M4x0.7 4.0 0.70 3.30 #30 4.5 #16
M5x0.8 5.0 0.80 4.20 #19 5.5 7/32
M6x1 6.0 1.00 5.0 #8 6.6 G
M8x1.25 8.0 1.25 6.8 H 9.0 T
M8x1 8.0 1.00 7.0 J 9.0 T
M10x1.5 10.0 1.50 8.5> R 12.0 31/64
M10x1.25 10.0 1.25 8.8 11/32 12.0 31/64
M12x1.75 12.0 1.75 10.2 13/32 14.0 35/64
M12x1.25 12.0 1.25 10.8 27/64 14.0 35/64
M14x2 14.0 2.00 12.0 15/32 16.0 5/8
M14x1.5 14.0 1.5 12.5 1/2 16.0 5/8
M16x2 16.0 2.00 14.0 35/64 18.0 45/64
M16x1.5 16.0 1.50 14.5 37/64 18.0 45/64
M18x2.5 18.0 2.50 15.5 39/64 20.0 51/64
M18x1.5 18.0 1.50 16.5 21/32 20.0 51/64
M20x2.5 20.0 2.50 17.5 11/16 22.0 7/8
M20x1.5 20.0 1.50 18.5 47/64 22.0 7/8
M22x2.5 22.0 2.50 19.5 49/64 25.0 1
M22x1.5 22.0 1.50 20.5 13/16 25.0 1
M24x3 24.0 3.00 21.0 53/64 27.0 1-5/64
M24x2 24.0 2.00 22.0 7/8 27.0 1-5/64
M27x3 27.0 3.00 24.0 15/16 30.0 1-3/16
M27x2 27.0 2.0 25.0 1 30.0 1-3/16

Standard UNC Tap Drill Sizes
Standard UNF Tap Drill Sizes
Standard NPT Tap Drill Sizes

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Tap Drill Size – UNF

Below is a table of drill and tap sizes for Unified Screw Threads – Fine, UNF.

UNF screws may not always be appropriate.  Depending on the application, you may be better off using UNC fasteners.


INCH SIZES – NATIONAL FINE
TAP SIZE DRILL SIZE
#1-72 #53
#2-64 #50
#3-56 #46
#4-48 #42
#5-44 #37
#6-40 #33
#8-36 #29
#10-32 #21
#12-28 #15
1/4-28 #3
5/16-24 I
3/8-24 Q
7/16-20 W
1/2-20 29/64
9/16-18 33/64
5/8-18 37/64
3/4-16 11/16
7/8-14 13/16
1″-12 15/16
1-1/8-12 1-3/64
1-1/4-12 1-11/64
1-1/2-12 1-27/64
1-3/4-12 1-43/64
2″-12 1-59/64

Metric Tap Drill Sizes
Standard UNC Tap Drill Sizes
Standard NPT Tap Drill Sizes

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Tap Drill Size – UNC

Below is a table of drill and tap sizes for Unified Screw Threads – Course, UNC.

UNC screws may not always be appropriate.  Depending on the application, you may be better off using UNF fasteners.


INCH SIZES – NATIONAL COARSE
TAP SIZE DRILL SIZE
#0-80 3/64″
#1-64 #53
#2-56 #51
#3-48 5/64″
#4-40 #43
#5-40 #39
#6-32 #36
#8-32 #29
#10-24 #25
#12-24 #17
1/4-20 #7
5/16-18 F
3/8-16 5/16
7/16-14 U
1/2-13 27/64
9/16-12 31/64
5/8-11 17/32
3/4-10 21/32
7/8-9 49/64
1″-8 7/8
1-1/8-7 63/64
1-1/4-7 1-7/64
1-1/2-6 1-11/32
1-3/4-5 1-35/64
2″-4-1/2 1-25/32

Metric Tap Drill Sizes
Standard UNF Tap Drill Sizes
Standard NPT Tap Drill Sizes