DESCRIPTION SIZE
(mm)		 SIZE
(inches)		 FRACTION
(inches)		 NUMBER,
or,
LETTER		 STANDARD,
METRIC,
SIZE
_ 0.2 0.0079 _ _ _
_ 0.22 0.0087 _ _ _
_ 0.25 0.0098 _ _ _
_ 0.28 0.0110 _ _ _
_ 0.3 0.0118 _ _ _
_ 0.32 0.0126 _ _ _
_ 0.35 0.0138 _ 80 0.35
_ 0.38 0.0150 _ 79 0.38
_ 0.39 0.0156 1/64 _ _
_ 0.4 0.0157 _ 78 0.4
_ 0.42 0.0165 _ _ _
_ 0.45 0.0177 _ 77 0.45
_ 0.48 0.0189 _ _ _
_ 0.5 0.0197 _ 76 0.5
_ 0.52 0.0205 _ 75 0.52
_ 0.55 0.0217 _ _ _
_ 0.58 0.0228 _ 74 0.58
Tapping Drill 16 BA 0.6 0.0236 _ 73 0.6
_ 0.62 0.0244 _ 72 0.62
_ 0.65 0.0256 _ 71 0.65
_ 0.68 0.0268 _ _ _
Tapping Drill 15 BA 0.7 0.0276 _ 70 0.7
_ 0.72 0.0283 _ _ _
Tapping Drill
ISO metric coarse
1 mm		 0.75 0.0295 _ 69 0.75
_ 0.78 0.0307 _ _ _
_ 0.79 0.0312 1/32 68 _
Tapping Drill 14 BA 0.8 0.0315 _ _ _
_ 0.82 0.0323 _ 67 0.82
Tapping Drill
ISO Metric Coarse
1.1 mm		 0.85 0.0335 _ 66 0.84
_ 0.88 0.0346 _ _ _
_ 0.9 0.0354 _ 65 0.9
_ 0.92 0.0362 _ 64 0.92
Tapping Drill
ISO Metric Coarse
1.2 mm		 0.95 0.0374 _ 63 0.96
Tapping Drill 13 BA 0.98 0.0386 _ 62 0.98
Tapping Drill 12 BA
and 17swg CEI		 1 0.0394 _ 61 1
Tapping Drill 12 BA 1.05 0.0413 _ 60 1.02
Tapping Dnll
ISO Metric Coarse
1.4 mm		 1.1 0.0433 _ 59 1.05
_ 1.15 0.0453 _ 58 1.07
Tapping Drill 16swg CEI 1.19 0.0469 3/64 57 1.1
Tapping Drill 11 BA
and 1/16 Whitworth		 1.2 0.0472 _ 56 _
Tapping Dnll
ISO Metric Coarse
1.6 mm
and No 0 UNF		 1.25 0.0492 _ _ _
_ 1.3 0.0512 _ 55 1.3
Tapping Drill
ISO Metric
Special Pitches
1.7 mm		 1.35 0.0531 _ _ _
Tapping Drill
15swg CEI
and 10BA		 1.4 0.0551 _ 54 1.4
Tapping Drill
ISO Metric Coarse
1.8 mm		 1.45 0.0571 _ _ _
Tapping Drill 9 BA 1.5 0.0591 _ 53 1.52
Tapping Drill
ISO Metric Special Pitches
2 mm
and No1 UNC		 1.55 0.0610 _ _ _
_ 1.58 0.0625 1/16 _ _
Tapping Drill
ISO Metric Coarse 2 mm,
No1 UNF
and 14swg CEI		 1.6 0.0630 _ 52 1.62
_ 1.65 0.0650 _ _ _
_ 1.7 0.0669 _ 51 1.7
Tapping Drill
ISO Metric Coarse
2.2 mm		 1.75 0.0689 _ _ _
Tapping Drill 8 BA 1.8 0.0709 _ 50 1.8
Tapping Drill 3/32 Whitworth,
No2 UNC
and 13swg CEI		 1.85 0.0728 _ 49 1.85
Tapping Drill
ISO Metric Special Pitches
2.3 mm
and No2 UNF		 1.9 0.0748 _ 48 1.92
_ 1.95 0.0768 _ _ _
_ 1.98 0.0781 5/64 _ _
Tapping Drill 7 BA 2 0.0787 _ 47 2
Tapping Drill
ISO Metric Coarse 2.5 mm
and 12swg CEI		 2.05 0.0807 _ 46 2.05
Tapping Drill No3 UNC 2.1 0.0827 _ 45 2.1
Tapping Drill
ISO Metric Special Pitches
2.6 mm
and No3 UNF		 2.15 0.0846 _ _ _
_ 2.2 0.0866 _ 44 2.2
_ 2.25 0.0886 _ 43 2.25
Tapping Drill 6 BA 2.3 0.0906 _ _ _
Tapping Drill No4 UNC 2.35 0.0925 _ _ _
_ 2.38 0.0938 3/32 42 _
Tapping Drill
ISO Metric Special Pitches
3 mm
and No4 UNF		 2.4 0.0945 _ _ _
_ 2.45 0.0965 _ 41 2.45
Tapping Drill
ISO Metric Coarse
3 mm		 2.5 0.0984 _ 40 2.5
Tapping Drill 1/8 Whitworth
1/8 BSC
and 1/8 CEI		 2.55 0.1004 _ 39 2.55
Tapping Drill 5 BA 2.6 0.1024 _ 38 2.6
Tapping Drill
ISO Metric Fine
3 mm
and No5 UNC		 2.65 0.1043 _ 37 2.65
Tapping Drill No5 UNF 2.7 0.1063 _ 36 2.7
_ 2.75 0.1083 _ _ _
_ 2.78 0.1094 7/64 _ _
_ 2.8 0.1102 _ 35 2.8
Tapping Drill No6 UNC 2.85 0.1122 _ 34 2.82
Tapping Drill
ISO Metric Coarse
3.5 mm		 2.9 0.1142 _ 33 2.85
Tapping Drill 4 BA
and No6 UNF		 2.95 0.1161 _ 32 2.95
_ 3 0.1181 _ 31 3.05
_ 3.1 0.1220 _ _ _
_ 3.18 0.1250 1/8 _ _
Tapping Drill 5/32 BSC,
5/32 Whitworth,
ISO Metric Special Pitches
2.3 mm
and 0.154 CEI		 3.2 0.1260 _ 30 3.25
Tapping Drill
ISO Metric Coarse
4 mm		 3.3 0.1299 _ _ _
Tapping Drill 3 BA 3.4 0.1339 _ 29 3.45
Tapping Drill
ISO Metric Fine
4 mm
and No8 UNC		 3.5 0.1378 _ _ _
Tapping Drill No8 UNF 3.55 0.1398 _ _ _
_ 3.57 0.1406 9/64 28 _
Tapping Drill 0.175 CEI 3.6 0.1417 _ 27 3.65
Tapping Drill 3/16 Whitworth 3.7 0.1457 _ 26 3.7
Tapping Drill
ISO Metric Coarse
4.5 mm		 3.8 0.1496 _ 25 3.8
Tapping Drill No10 UNC 3.9 0.1535 _ 24 3.9
Tapping Drill 3/16 BSF
3/16 CEI
and 3/16 BSC		 3.97 0.1562 5/32 23 3.92
Tapping Drill 2 BA 4 0.1575 _ 22 4
Tapping Drill
ISO Metric Special Pitches
5 mm
and No 10 UNF		 4.1 0.1614 _ 21 4.02
Tapping Drill
ISO Metric Coarse
5 mm		 4.2 0.1654 _ 20 4.1
_ 4.3 0.1693 _ 19 4.2
_ 4.37 0.1719 11/64 18 4.3
_ 4.4 0.1732 _ 17 4.4
Tapping Drill 1 BA,
7/32 Whitworth,
and ISO Metric Fine
5 mm		 4.5 0.1772 _ 16 4.5
Tapping Drill No12 UNC 4.55 0.1791 _ _ _
Tapping Drill 7/32 BSF
and ISO Metric Special Pitches
5.5 mm		 4.6 0.1811 _ 15 4.58
Tapping Drill No 12 UNF 4.65 0.1831 _ _ _
_ 4.7 0.1850 _ 14 4.62
_ 4.76 0.1875 3/16 13 4.7
_ 4.8 0.1890 _ 12 4.8
_ 4.9 0.1929 _ 11 4.85
Tapping Drill
ISO Metric Coarse
6 mm		 5 0.1969 _ 10 4.9
Tapping Drill 0 BA
and 1/4 Whitworth		 5.1 0.2008 _ 9 5
_ 5.16 0.2031 13/64 8 5.08
Tapping Drill 1/4 UNC
and ISO Metric Fine
6 mm		 5.2 0.2047 _ 7 5.1
Tapping Drill 1/4 BSF 5.3 0.2087 _ 6 5.2
_ 5.4 0.2126 _ 5 5.22
Tapping Drill 1/4 UNF 5.5 0.2165 _ 4 5.3
Tapping Drill 1/4 BSC
and 1/4 CEI		 5.56 0.2188 7/32 3 5.4
_ 5.6 0.2205 _ 2 5.6
_ 5.7 0.2244 _ _ _
Tapping Drill 0.266 CEI 5.8 0.2283 _ 1 5.8
_ 5.9 0.2323 _ A 5.85
_ 5.95 0.2344 15/64 _ _
Tapping Drill,
ISO Metric Coarse,
7 mm
and 9/32 BSF		 6 0.2362 _ B 6.05
_ 6.1 0.2402 _ C 6.15
Tapping Drill 9/32 BSC,
0.281 CEI,
and ISO Metric Fine,
7 mm		 6.2 0.2441 _ D 6.25
_ 6.3 0.2480 _ E 6.35
_ 6.35 0.2500 1/4 _ _
Tapping Drill 1/16 BSTP 6.4 0.2520 _ _ _
Tapping Drill 5/16 Whitworth 6.5 0.2559 _ F 6.55
Tapping Drill 5/16 UNC
and 1/16 BSP		 6.6 0.2598 _ G 6.65
_ 6.7 0.2638 _ H 6.76
Tapping Drill 5/16 BSF 6.75 0.2655 17/64 _ _
Tapping Drill
ISO Metric Coarse
8 mm		 6.8 0.2677 _ _ _
Tapping Drill 5/16 UNF 6.9 0.2717 _ I 6.95
Tapping Drill 5/16 BSC,
ISO Metric Fine
8 mm
and 5/16 CEI		 7 0.2756 _ J 7.05
_ 7.1 0.2795 _ K 7.15
_ 7.14 0.2812 9/32 _ _
Tapping Drill
ISO Metric Special Pitches
8 mm		 7.2 0.2835 _ _ _
_ 7.3 0.2874 _ L 7.35
_ 7.4 0.2913 _ M 7.45
_ 7.5 0.2953 _ _ _
_ 7.54 0.2969 19/64 _ _
_ 7.6 0.2992 _ N 7.65
_ 7.7 0.3031 _ _ _
Tapping Dnll
ISO Metric Coarse
9 mm		 7.8 0.3071 _ _ _
_ 7.9 0.3110 _ _ _
Tapping Drill 3/8 Whitworth 7.94 0.3125 5/16 _ _
Tapping Drill 3/8 UNC
and ISO Metric Special Pitches
9 mm		 8 0.3150 _ 0 8.05
_ 8.1 0.3189 _ _ _
Tapping Drill 3/8 BSF 8.2 0.3228 _ P 8.2
_ 8.3 0.3268 _ _ _
_ 8.33 0.3281 21/64 _ _
Tapping Drill 1/8 BSTP 8.4 0.3307 _ Q 8.46
Tapping Drill
ISO Metric Coarse
10 mm
and 3/8 UNF		 8.5 0.3346 _ _ _
Tapping Drill 3/8 BSC
and 3/8 CEI		 8.6 0.3386 _ R 8.65
_ 8.7 0.3425 _ _ _
Tapping Drill 1/8 BSP 8.73 0.3438 11/32 _ _
Tapping Drill
ISO Metric Fine
10 mm		 8.8 0.3465 _ 5 8.85
_ 8.9 0.3504 _ _ _
Tapping Drill
ISO Metric Special Pitches
10 mm (1mm Pitch)		 9 0.3543 _ _ _
_ 9.1 0.3583 _ T 9.1
_ 9.13 0.3594 23/64 _ _
Tapping Drill
ISO Metric Special Pitches
10 mm (0.75mm Pitch)		 9.2 0.3622 _ _ _
Tapping Drill 7/16 Whitworth 9.3 0.3661 _ U 9.35
Tapping Drill 7/16 UNC 9.4 0.3701 _ _ _
Tapping Dnll
ISO Metric Coarse
11 mm		 9.5 0.3740 _ V 9.55
_ 9.53 0.3750 3/8 _ _
_ 9.6 0.3780 _ _ _
Tapping Drill 7/16 BSF 9.7 0.3819 _ _ _
_ 9.8 0.3858 _ W 9.8
Tapping Drill 7/16 UNF 9.9 0.3898 _ _ _
_ 9.92 0.3906 25/64 _ _
_ 10 0.3937 _ _ _
Tapping Drill 7/16 BSC 10.1 0.3976 _ X 10.1
Tapping Drill
ISO Metric Coarse
12 mm		 10.2 0.4016 _ _ _
_ 10.3 0.4055 _ Y 10.3
_ 10.32 0.4062 13/32 _ _
_ 10.4 0.4094 _ _ _
Tapping Drill 1/2 Whitworth
and ISO Metric
Special Pitches
12 mm
(1.5 mm pitch)		 10.5 0.4134 _ Z 10.5
_ 10.6 0.4173 _ _ _
_ 10.7 0.4213 _ _ _
_ 10.72 0.4219 27/64 _ _
Tapping Drill 1/2 UNC
and ISO Metric Fine
12 mm (1.25 mm Pitch)		 10.8 0.4252 _ _ _
_ 10.9 0.4291 _ _ _
Tapping Drill
ISO Metric Special Pitches
12 mm
(1mm pitch)		 11 0.4331 _ _ _
_ 11.1 0.4370 _ _ _
Tapping Drill 1/2 BSF 11.11 0.4375 7/16 _ _
Tapping Drill 1/4 BSTP 11.2 0.4409 _ _ _
_ 11.3 0.4449 _ _ _
Tapping Drill 1/2 UNF 11.4 0.4488 _ _ _
_ 11.5 0.4528 _ _ _
_ 11.51 0.4531 29/64 _ _
_ 11.6 0.4567 _ _ _
_ 11.7 0.4606 _ _ _
Tapping Drill 1/4 BSP 11.8 0.4646 _ _ _
_ 11.9 0.4685 _ _ _
_ 11.91 0.4688 15/32 _ _
Tapping Drill
ISO Metric Coarse
14 mm		 12 0.4724 _ _ _
Tapping Drill 9/16 Whitworth 12.1 0.4764 _ _ _
Tapping Drill 9/16 UNC 12.2 0.4803 _ _ _
_ 12.3 0.4843 _ _ _
_ 12.3 0.4844 31/64 _ _
_ 12.4 0.4882 _ _ _
Tapping Drill
ISO Metric Special Pitches
14 mm		 12.5 0.4921 _ _ _
_ 12.6 0.4961 _ _ _
Tapping Drill 9/16 BSF 12.7 0.5000 1/2 _ _
Tapping Drill
ISO Metric Fine
14 mm (1.25 mm Pitch)		 12.8 0.5039 _ _ _
Tapping Drill 9/I 6 UNF 12.9 0.5079 _ _ _
_ 13 0.5118 _ _ _
Tapping Drill 9/16 BSC
and 9/16 CEI		 13.1 0.5156 33/64 _ _
_ 13.1 0.5157 _ _ _
_ 13.2 0.5197 _ _ _
_ 13.3 0.5236 _ _ _
_ 13.4 0.5276 _ _ _
Tapping Drill 5/8 UNC 13.49 0.5313 17/32 _ _
Tapping Drill 5/8 Whitworth 13.5 0.5315 _ _ _
_ 13.6 0.5354 _ _ _
_ 13.7 0.5394 _ _ _
_ 13.8 0.5433 _ _ _
_ 13.89 0.5469 35/64 _ _
_ 13.9 0.5472 _ _ _
Tapping Drill
ISO Metric Coarse
16 mm
and 5/8 BSF		 14 0.5512 _ _ _
_ 14.25 0.5610 _ _ _
_ 14.3 0.5625 9/16 _ _
Tapping Drill 5/8 UNF
and ISO Metric Fine
16 mm		 14.5 0.5709 _ _ _
_ 14.68 0.5780 37/64 _ _
Tapping Drill 3/8 BSTP 14.75 0.5807 _ _ _
Tapping Drill 11/16 Whitworth,
ISO Metric Special Pitches
16 mm
and 5/8 BSC		 15 0.5906 _ _ _
_ 15.08 0.5937 19/32 _ _
Tapping Drill 3/8 BSP 15.25 0.6004 _ _ _
_ 15.48 0.6094 39/64 _ _
Tapping Drill
ISO Metric Coarse 18 mm
and 11/16 BSF		 15.5 0.6102 _ _ _
_ 15.75 0.6201 _ _ _
_ 15.88 0.6252 5/8 _ _
_ 16 0.6299 _ _ _
_ 16.25 0.6398 _ _ _
Tapping Drill 3/4 Whitworth 16.27 0.6406 41/64 _ _
Tapping Drill 3/4 UNC
and ISO Metric Fine
18 mm		 16.5 0.6496 _ _ _
_ 16.67 0.6563 21/32 _ _
Tapping Drill 3/4 BSF 16.75 0.6594 _ _ _
_ 17 0.6693 _ _ _
_ 17.07 0.6720 43/64 _ _
_ 17.25 0.6791 _ _ _
Tapping Drill 3/4 UNF 17.46 0.6874 11/16 _ _
Tapping Drill
ISO Metric Coarse
20 mm		 17.5 0.6890 _ _ _
_ 17.75 0.6988 _ _ _
_ 17.86 0.7031 45/64 _ _
Tapping Drill 13/16 Whitworth
and ISO Metric Special Pitches
20 mm (2 mm pitch)		 18 0.7087 _ _ _
Tapping Drill 1/2 BSTP 18.25 0.7185 _ _ _
_ 18.26 0.7189 23/32 _ _
Tapping Drill
ISO Metric Fine
20 mm (1.5 mm Pitch)		 18.5 0.7283 _ _ _
_ 18.65 0.7343 47/64 _ _
_ 18.75 0.7382 _ _ _
Tapping Drill
ISO Metric Special Pitches
20 mm
(1 mm pitch)		 19 0.7480 _ _ _
Tapping Drill 1/2 BSP 19.05 0.7500 3/4 _ _
Tapping Drill 7/8 Whitworth 19.25 0.7579 _ _ _
Tapping Drill 7/8 UNC 19.45 0.7656 49/64 _ _
Tapping Drill
ISO Metric Coarse
22 mm		 19.5 0.7677 _ _ _
_ 19.75 0.7776 _ _ _
Tapping Drill 7/8 BSF 19.84 0.7812 25/32 _ _
_ 20 0.7874 _ _ _
_ 20.24 0.7969 51/64 _ _
_ 20.25 0.7972 _ _ _
Tapping Drill
ISO Metric Fine
22 mm		 20.5 0.8071 _ _ _
Tapping Drill 7/8 UNF 20.64 0.8125 13/16 _ _
Tapping Drill 15/16 Whitworth 20.75 0.8169 _ _ _
Tapping Drill
ISO Metric Coarse
24 mm		 21 0.8268 _ _ _
Tapping Drill 5/8 BSP 21.03 0.8281 53/64 _ _
_ 21.25 0.8366 _ _ _
_ 21.43 0.8438 27/32 _ _
_ 21.5 0.8465 _ _ _
_ 21.75 0.8563 _ _ _
_ 21.83 0.8594 55/64 _ _
Tapping Drill 1 inch Whitworth
and ISO Metric Fine
24 mm		 22 0.8661 _ _ _
_ 22.23 0.8750 7/8 _ _
Tapping Drill I inch UNC 22.25 0.8760 _ _ _
Tapping Drill
ISO Metric Special Pitches
24 mm
(1.5 mm pitch)		 22.5 0.8858 _ _ _
Alternative Tapping Drill
I inch BSF		 22.62 0.8906 57/64 _ _
Tapping Drill 1 inch BSF 22.75 0.8957 _ _ _
Tapping Drill
ISO Metric Special Pitches
24 mm
(1 mm pitch)		 23 0.9055 _ _ _
_ 23.02 0.9062 29/32 _ _
Tapping Drill I UNF 23.25 0.9154 _ _ _
_ 23.42 0.9219 59/64 _ _
Tapping Drill
ISO Metric Special Pitches
25 mm
(1.5 mm pitch)		 23.5 0.9252 _ _ _
Tapping Drill 3/4 BSTP 23.75 0.9350 _ _ _
_ 23.81 0.9375 15/16 _ _
Tapping Drill
ISO Metric Coarse
27 mm		 24 0.9449 _ _ _
_ 24.21 0.9531 61/64 _ _
_ 24.25 0.9547 _ _ _
Tapping Drill 3/4 BSP 24.5 0.9646 _ _ _
Tapping Drill 1inch BSC
and 1 inch CEI		 24.61 0.9688 31/32 _ _
_ 24.75 0.9744 _ _ _
Tapping Drill
ISO Metric Fine
27 mm		 25 0.9843 _ _ _
_ 25 0.9844 63/64 _ _
_ 25.4 1.0000 1 _ _
_ _ _ _ _ _
Standards rise in Increments
of 1/64in and 0.50 mm.		 _ _ _ _ _

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