Tech Tips Index RASK CYCLE  TECH TIPS
Tap Drill Sizes
(National Course of U.S.S Threads)

Tap Drill Sizes
(National Fine or S.A.E)

Decimal Equivalent Size of the Letter Drills

Screw/Tap Size Threads per Inch Use Drill Number Screw/Tap Size Threads per Inch Use Drill Number Letter Drill Decimal Equivalent Letter Drill Decimal Equivalent
no. 5 40 39 no. 5 44 37 A .234 N .302
no. 6 32 36 no. 6 40 33 B .238 O .316
no. 8 32 29 no. 8 36 29 C .242 P .323
no. 10 24 25 no. 10 32 21 D .246 Q .332
no.12 24 17 no. 12 28 15 E .250 R .339
1/4 20 8 1/4 28 3 F .257 S .348
5/16 18 F 5/16 24 1 G .261 T .358
3/8 16 5/16 3/8 24 Q H .266 U .368
7/16 14 U 7/16 20 W I .272 V .377
1/2 13 27/64 1/2 20 29/64 J .277 W .386
9/16 12 31/64 9/16 18 33/64 K .281 X .397
5/8 11 17/32 5/8 18 37/64 L .290 Y .404
3/4 10 21/32 3/4 16 11/16 M .295 Z .413
1/8 9 49/64 7/8 14 13/16
 
1 8 7/8 1-1/8 12 1-3/64
1-1/8 7 63/64 1-1/4 12 1-11/64
1-1/4 7 1-7/64 1-1/2 12 1-27/64
1-1/2 6 1-11/32  
   
 DECIMAL  EQUIVALENT  SIZE  OF  THE  NUMBER  DRILLS 
Drill
#
   Decimal   Drill #  Decimal   Drill #   Decimal    Drill # Decimal   Drill #  Decimal  
80 .0135   64 .0360   48 .0760   32 .1160   16 .1770
79 .0145   63 .0370   47 .0785   31 .1200   15 .1800
78 .0160   62 .0380   46 .0810   30 .1285   14 .1820
77 .0180   61 .0390   45 .0820   29 1360   13 .1850
76 0.200   60 .0400   44 .0860   28 .1405   12 .1890
75 .0210   59 .0410   43 .0890   27 .1440   11 .1910
74 .0225   58 .0420   42 .0935   26 .1470   10 .1935
73 .0240   57 .0430   41 .0960   25 .1495   9 .1960
72 .0250   56 .0465   40 .0980   24 .1520   8 .1990
71 .0260   55 .0520   39 .0995   23 .1540   7 .2010
70 .0280   54 .0550.0595   38 .1015   22 .1570   6 .2040
69 .0292   53 .0595   37 .1040   21 .1590   5 .2055
68 .0310   52 .0635   36 .1065   20 .1670   4 .2090
67 .0320   51 .0670   35 .1100   19 .1660   3 .2130
66 .0330   50 .0700   34 .1110   18 .1695   2 .2210
65 .0350   49 .0730   33 .1130   17 .1730   1 .2280