Tap & Drill Chart

UNC - UNIFIED NATIONAL COARSE

Size - Imperial Threads Per Inch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
#1 64 1.50 53 1.55  
#2 56 1.85 50 1.80  
#3 48 2.10 47 2.05 5/64
#4 40 2.35 3/32 2.30 43
#5 40 2.65 38 2.60  
#6 32 2.85 36 2.80 7/64
#8 32 3.50 29 3.40  
#10 24 3.90 25 3.00 5/32
#12 24 4.50 16 4.40 11/64
1/4 20 5.20 13/64 5.10 7
5/16 18 6.60 17/64 6.50 F
3/8 16 8.10 5/16 8.00  
7/16 14 9.50 3/8 9.40 23/64
1/2 13 11.00 27/64 10.80  
9/16 12 12.20 31/64    
5/8 11 13.80 35/64 13.50 17/32
3/4 10   21/32 16.50 41/64
7/8 9 19.50 49/64    
1 8   7/8 22.50  
1-1/8 7   63/64 25.00  
1-1/4 7   1-7/6 28.00  
1-3/8 6 31.00 1-7/32 30.75 1-13/64
1-1/2 6   1-11/32 34.00 1-21/64
1-3/4 5   1-9/16 39.50  
2 4-1/2   1-25/32 45.00  

UNF - UNIFIED NATIONAL FINE

Size - Imperial Threads Per Inch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
#0 80 1.25 3/64    
#1 72 1.55 53    
#2 64 1.90 50    
#3 56 2.15 45    
#4 48 2.40 42   3/32
#5 44 2.70 37 2.65  
#6 40 2.95 33 2.90  
#8 36 3.60 9/64 3.50 29
#10 32 4.10 21 4.00 5/32
#12 28 4.70 14 4.60  
1/4 28 5.50 7/32 5.40 3
5/16 24 6.90 17/64 6.80 1
3/8 24 8.50 Q 8.40 21/64
7/16 20 10.00 25/64 9.80  
1/2 20 11.50 29/64    
9/16 18 12.90 33/64 12.80  
5/8 18 14.50 37/64    
3/4 16 17.50 11/16    
7/8 14 20.40 13/16 20.50  
1 12 23.25 59/64 23.50  
1 14* 23.50 15/16    
1-1/8 12 26.50 1-3/64    
1-1/4 12 29.50 1-11/64    
1-3/8 12 33.00 1-19/64    
1-1/2 12 36.00 1-27/64    

*1-12 Thread is UNF
standard, however 1-14
is popular demand and
generally stocked in
place of 1-12.

METRIC COARSE

Size - MM
Pitch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
1.6 0.35 1.25 3/64    
1.7 0.35 1.35 55    
1.8 0.35 1.45 54    
2 0.40 1.60 1/16    
2.5 0.45 2.05 46    
3 0.50 2.50 40    
3.5 0.60 2.90 33    
4 0.70 3.30 30    
4.5 0.75 3.70 27    
5 0.80 4.30 11/64 4.20 19
6 1.00 5.10 13/64 5.00 9
7 1.00 6.10   6.00 15/64
8 1.25 6.90 H 6.80 17/64
9 1.25 7.90 5/16 7.80  
10 1.50 8.60 11/32 8.50 Q
11 1.50 9.50 3/8    
12 1.75   13/32 10.20 Y
14 2.00 12.20 31/64 12.00 15/32
16 2.00 14.25 9/16 14.00 35/64
18 2.50 15.75   15.50 39/64
20 2.50   45/64 17.50 11/16
22 2.50   23/32 19.50 49/64
24 3.00 21.00 53/64    
27 3.00 24.00 61/64   15/16
30 3.50 26.50 1-3/64    
33 3.50   1-11/64   1-5/32
36 4.00   1-17/64 29.50 1-1/4
39 4.00 35.00 1-3/8 32.00  

METRIC FINE

Size - MM Pitch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
4 0.50 3.50 29   9/64
5 0.50 4.50 16    
6 0.75 5.25 5    
7 0.75 6.25 D 6.2 1/4
8 1.00 7.00 J 7.1 9/32
10 1.25 8.75 11/32   S
10 1.00 9.00 T   23/64
12 1.50 10.50 27/64   Z
12 1.25 27/64      
12 1.00 11.00 7/16    
14 1.50 12.50 31/64   1/2
16 1.50 14.75 37/64 14.5 9/16
18 2.00 16.00 5/8    
18 1.50 16.50 21/32 16.5  
20 2.00 18.00 45/64    
20 1.50 18.50 47/64    
22 2.00 20.00 25/32    
22 1.50 20.50 13/16 20.5  
24 2.00 22.00 7/8    
24 1.50 22.50 7/8    

BSW - BRITISH STANDARD WHITWORTH

Size - Imperial Threads Per Inch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
1/16 60 1.20 3/64 1.05  
3/32 48 1.90 49 1.75  
1/8 40 2.55   2.50 3/32
5/32 32 3.20 1/8 2.95  
3/16 24 3.70   3.60 9/64
7/32 24 4.50   4.30 11/64
1/4 20 5.10   5.00 3/16
5/16 18 6.50   6.40 1/4
3/8 16 7.90 5/16 7.80 19/64
7/16 14 9.50   9.20 23/64
1/2 12 10.50     13/32
9/16 12     12.00 15/32
5/8 11 13.50 17/32   33/64
3/4 10 16.50 41/64 16.00 5/8
7/8 9   3/4 19.00 47/64
1 8 22.00 55/64   27/32
1-1/8 7   31/32 24.50 61/64
1-1/4 7 28.00 1-3/32 27.50 1-5/64
1-1/2 6 33.50 1-5/16 33.00 1-19/64
1-3/4 5 39.00 1-17/32 38.50 1-33/64
2 1-1/2 44.50 1-49/64 44.00 1-3/4

BSF - BRITISH STANDARD FINE

Size - Imperial Threads Per Inch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
3/16 32 4.00 5/32 3.90  
1/4 26 5.30   5.20 13/64
5/16 22 6.80 17/64 6.70  
3/8 20 8.30 21/64 8.20 5/16
7/16 18     9.50 3/8
1/2 16   7/16 11.00 27/64
9/16 16   1/2 12.50 31/64
5/8 14 14.00 35/64 13.80 17/32
3/4 12     16.50 21/32
7/8 11   25/32 19.50 49/64
1 10   57/64 22.50 7/8
1-1/4 9 28.50 1-1/8   1-7/64
1-1/2 8 34.50 1-23/64   1-11/32
1-3/4 7 40.50 1-19/32 40.00 1-37/64

NPT - NATIONAL PIPE TAPER

Size - Imperial Threads Per Inch TAPPING DRILL SIZE
Preferred Alternative
mm inch mm inch
 1/16 27   D 6.30 1/4
1/8 27   R 8.70 11/32
1/4 18   7/16 11.10  
3/8 18   9/16 14.50 37/64
1/2 14   23/32 18.00  
3/4 14   59/64 23.25 15/16
1 11-1/2   1-5/32 29.00  
1-1/4 11-1/2   1-1/2 38.00  
1-1/2 11-1/2   1-47/64 44.00  
2 11-1/2   2-7/32 56.00  
2-1/2 8   2-5/8 67.00  
3 8   3-1/4 82.50  

 

DRILL SIZE DEC EQUIV. MM   DRILL SIZE DEC EQUIV. MM   DRILL SIZE DEC EQUIV. MM   DRILL SIZE DEC EQUIV. MM
- .0039 0.10   45 .0820 2.08   4 .2090 5.31   15/32 .4688 11.91
- .0079 0.20   44 .0860 2.18   3 .2130 5.41   - .4724 12.00
- .0098 0.25   43 .0890 2.26   7/32 .2188 5.56   31/64 .4844 12.30
- .0118 0.30   42 .0935 2.37   2 .2210 6.61   1/2 .5000 12.70
80 .0135 0.34   3/32 .0938 2.38   1 .2280 5.79   - .5118 13.00
79 .0145 0.37   41 .0960 2.44   A .2340 5.94   33/64 .5156 13.10
1/64 .0156 0.40   40 .0980 2.5   15/64 .2344 5.95   17/32 .5312 13.49
78 .0160 0.41   39 .0995 2.53   - .2362 6.00   35/64 .5469 13.89
77 .0181 0.46   38 .1015 2.58   B .2380 6.05   - .5512 14.00
- 0.197 0.50   37 .1040 2.64   C .2420 6.15   9/16 .5625 1429
76 .0200 0.51   36 .1065 2.71   D .2460 6.25   37/64 .5781 14.68
75 .0210 0.53   7/64 .1094 2.78   1/4 .2500 6.35   - .5906 15.00
74 .0225 0.57   35 .1100 2.79   E .2500 6.35   19/32 .5938 15.08
- .0236 0.60   34 .1110 2.79   F .2570 6.53   39/64 .6094 15.48
73 .0240 0.61   33 .1130 2.87   G .2610 6.63   5/8 .6250 15.88
72 .0250 0.64   32 .1160 2.95   17/64 .2656 6.75   - .6299 16.00
71 .0260 0.66   - .1181 3.00   H .2660 6.76   41/64 .6406 16.27
- .0276 0.70   31 .1200 3.05   I .2720 6.91   21/32 .6562 16.67
70 .0280 0.71   1/8 .1250 3.18   - .2756 7.00   - .6693 17.00
69 .0292 0.74   30 .1285 3.26   J .2770 7.04   43/64 .6719 17.07
- .0295 0.75   29 .1360 3.45   K .2810 7.14   11/16 .6875 17.46
68 .0310 0.79   28 .1405 3.57   9/32 .2812 7.14   45/64 .7031 17.88
1/32 .0313 0.79   9/64 .1406 3.57   L .2900 7.37   - .7087 18.00
- .0315 0.80   27 .1440 3.66   M .2950 7.49   23/32 .7188 18.26
67 .0320 0.81   26 .1470 3.73   19/64 .2969 7.54   47/64 .7344 18.65
66 .0330 0.84   25 .1495 3.80   N .3020 7.67   - .7344 18.65
65 .0350 0.89   24 .1520 3.86   5/16 .3125 7.94   3/4 .7500 19.05
- .0354 0.90   23 .1540 3.91   - .3150 8.00   49/64 .7656 19.45
64 .0360 0.91   5/32 .1562 3.97   O .3160 8.03   25/32 .7812 19.84
63 .0370 0.94   22 .1570 3.99   P .3230 8.20   - .7874 20.00
62 .0380 0.97   - .1575 4.00   21/64 .3281 8.33   51/64 .7969 20.24
61 .0394 0.99   21 .1590 4.04   Q .2230 8.43   13/16 .8125 20.64
- .0394 1.00   20 .1610 4.09   R .3390 8.61   - .8268 21.00
60 .0400 1.02   19 .1660 4.22   11/32 .3438 8.73   53/64 .8281 21.03
59 .0410 1.04   18 .1695 4.31   S .3480 8.84   27/32 .8438 21.43
58 .0420 1.07   11/64 .1719 4.37   - .3543 9.00   55/64 .8594 21.84
57 .0430 1.09   17 .1730 4.39   T .3580 9.09   - .8661 22.00
56 .0465 1.18   16 .1770 4.50   23/64 .3594 9.13   7/8 .8750 22.23
3/64 .0469 1.19   15 .1800 4.57   U .3680 9.35   57/64 .8906 22.62
55 .0520 1.32   14 .1820 4.62   3/8 .3750 9.35   - .9055 23.00
54 .0550 1.40   13 .1850 4.70   V .3770 9.56   29/32 .9062 23.02
53 .0595 1.51   3/16 .1875 4.76   W .3860 9.80   59/64 .9219 23.42
1/16 .0625 1.59   12 .1890 4.80   25/64 .3906 9.92   15/16 .9375 23.81
52 .0635 1.61   11 .1910 4.85   - .3937 10.00   - .9449 24.00
51 .0670 1.70   10 .1935 4.91   X .3970 10.08   61/64 .9531 24.21
50 .0700 1.78   9 .1960 4.98   Y .4040 10.26   31/32 .9688 24.61
49 .0730 1.85   - .1968 5.00   13/32 .4062 10.32   - .9842 25.00
48 .0760 1.93   8 .1990 5.05   Z .4130 10.49   63/64 .9844 25.00
5/64 .0781 1.98   7 .2010 5.11   27/64 .4219 10.72   1 1.00 25.40
47 .0785 1.99   13/64 .2031 5.16   - .4331 11.00        
- .0787 2.00   6 .2040 5.18   7/16 .4375 11.11        
46 .0810 1.06   5 .2055 5.22   29/64 .4531 11.51        

 

 

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