TAPPING 2029

Table 3. Tap Drill Sizes for Threads of American National Form

Screw Thread Commercial Tap Drillsa Screw Thread Commercial Tap Drillsa
Outside Size Outside Size
Root Decimal Root Decimal
Diam. or Diam. or
Diam. Equiv. Diam. Equiv.
Pitch Number Pitch Number
1⁄ -64 0.0422 3⁄ 0.0469 27 0.4519 15⁄ 0.4687
16 64 32

72 0.0445 3⁄ 0.0469 9⁄ -12 0.4542 31⁄ 0.4844

64 16 64
5⁄ -60 0.0563 1⁄ 0.0625 18 0.4903 33⁄ 0.5156
64 16 64
72 0.0601 52 0.0635 27 0.5144 17⁄ 0.5312
32
3⁄ -48 0.0667 49 0.0730 5⁄ -11 0.5069 17⁄ 0.5312
32 8 32

50 0.0678 49 0.0730 12 0.5168 35⁄ 0.5469

64
7⁄ -48 0.0823 43 0.0890 18 0.5528 37⁄ 0.5781
64 64
1⁄ -32 0.0844 3⁄ 0.0937 27 0.5769 19⁄ 0.5937
8 32 32
40 0.0925 38 0.1015 11⁄ -11 0.5694 19⁄ 0.5937
16 32
9⁄ -40 0.1081 32 0.1160 16 0.6063 5⁄ 0.6250
64 8
5⁄ -32 0.1157 1⁄ 0.1250 3⁄ -10 0.6201 21⁄ 0.6562
32 8 4 32
36 0.1202 30 0.1285 12 0.6418 43⁄ 0.6719
64
11⁄ -32 0.1313 9⁄ 0.1406 16 0.6688 11⁄ 0.6875
64 64 16
3⁄ -24 0.1334 26 0.1470 27 0.7019 23⁄ 0.7187
16 32
32 0.1469 22 0.1570 13⁄ -10 0.6826 23⁄ 0.7187
16 32
13⁄ -24 0.1490 20 0.1610 7⁄ -9 0.7307 49⁄ 0.7656
64 8 64
7⁄ -24 0.1646 16 0.1770 12 0.7668 51⁄ 0.7969
32 64
32 0.1782 12 0.1890 14 0.7822 13⁄ 0.8125
16
15⁄ -24 0.1806 10 0.1935 18 0.8028 53⁄ 0.8281
64 64
1⁄ -20 0.1850 7 0.2010 27 0.8269 27⁄ 0.8437
4 32
24 0.1959 4 0.2090 15⁄ - 9 0.7932 53⁄ 0.8281
16 64

27 0.2019 3 0.2130 1-8 0.8376 7⁄ 0.8750

8

28 0.2036 3 0.2130 12 0.8918 59⁄ 0.9219

64
32 0.2094 7⁄ 0.2187 14 0.9072 15⁄ 0.9375
32 16
5⁄ -18 0.2403 F 0.2570 27 0.9519 31⁄ 0.9687
16 32

20 0.2476 17⁄ 0.2656 11⁄8- 7 0.9394 63⁄ 0.9844

64 64
24 0.2584 I 0.2720 12 1.0168 13⁄64 1.0469
27 0.2644 J 0.2770 11⁄4- 7 1.0644 17⁄64 1.1094
32 0.2719 9⁄ 0.2812 12 1.1418 111⁄64 1.1719
32
3⁄ -16 0.2938 5⁄ 0.3125 13⁄8- 6 1.1585 17⁄32 1.2187
8 16

20 0.3100 21⁄ 0.3281 12 1.2668 119⁄64 1.2969

64

24 0.3209 Q 0.3320 11⁄2- 6 1.2835 111⁄32 1.3437

27 0.3269 R 0.3390 12 1.3918 127⁄64 1.4219
7⁄ -14 0.3447 U 0.3680 15⁄8- 51⁄2 1.3888 129⁄64 1.4531
16

20 0.3726 25⁄ 0.3906 13⁄4- 5 1.4902 19⁄16 1.5625

64
24 0.3834 X 0.3970 17⁄8- 5 1.6152 111⁄16 1.6875
27 0.3894 Y 0.4040 2 - 41⁄2 1.7113 125⁄32 1.7812
1⁄ -12 0.3918 27⁄ 0.4219 21⁄8- 41⁄2 1.8363 129⁄32 1.9062
2 64

13 0.4001 27⁄ 0.4219 21⁄4- 41⁄2 1.9613 21⁄32 2.0312

64

20 0.4351 29⁄ 0.4531 23⁄8- 4 2.0502 21⁄8 2.1250

64
24 0.4459 29⁄ 0.4531 21⁄2- 4 2.1752 21⁄4 2.2500
64

a These tap drill diameters allow approximately 75 per cent of a full thread to be produced. For small
thread sizes in the first column, the use of drills to produce the larger hole sizes shown in Table 2 will
reduce defects caused by tap problems and breakage.