Machinery's Handbook, 31st Edition
2168
Diameter of Tap Drill Table 4. Tap Drill Sizes for Threads of American National Form Screw Thread Commercial Tap Drills a Screw Thread
Commercial Tap Drills a
Outside Diam. Pitch
Size or Number
Outside Diam. Pitch
Size or Number
Root Diam. 0.0422 0.0445 0.0563 0.0601 0.0667 0.0678 0.0823 0.0844 0.0925 0.1081 0.1157 0.1202 0.1313 0.1334 0.1469 0.1490 0.1646 0.1782 0.1806 0.1850 0.1959 0.2019 0.2036 0.2094 0.2403 0.2476 0.2584 0.2644 0.2719 0.2938 0.3100 0.3209 0.3269 0.3447 0.3726 0.3834 0.3894 0.3918 0.4001 0.4351 0.4459
Decimal Equiv.
Root Diam. 0.4519 0.4542 0.4903 0.5144 0.5069 0.5168 0.5528 0.5769 0.5694 0.6063 0.6201 0.6418 0.6688 0.7019 0.6826 0.7307 0.7668 0.7822 0.8028 0.8269 0.7932 0.8376 0.8918 0.9072 0.9519 0.9394 1.0168 1.0644 1.1418 1.1585 1.2668 1.2835 1.3918 1.3888 1.4902 1.6152 1.7113 1.8363 1.9613 2.0502 2.1752
Decimal Equiv.
0.0469 0.0469 0.0625 0.0635 0.0730 0.0730 0.0890 0.0937 0.1015 0.1160 0.1250 0.1285 0.1406 0.1470 0.1570 0.1610 0.1770 0.1890 0.1935 0.2010 0.2090 0.2130 0.2130 0.2187 0.2570 0.2656 0.2720 0.2770 0.2812 0.3125 0.3281 0.3320 0.3390 0.3680 0.3906 0.3970 0.4040 0.4219 0.4219 0.4531
27
0.4687 0.4844 0.5156 0.5312 0.5312 0.5469 0.5781 0.5937 0.5937 0.6250 0.6562 0.6719 0.6875 0.7187 0.7187 0.7656 0.7969 0.8125 0.8281 0.8437 0.8281 0.8750 0.9219 0.9375 0.9687 0.9844 1.0469 1.1094 1.1719 1.2187 1.2969 1.3437 1.4219 1.4531 1.5625 1.6875 1.7812 1.9062 2.0312 2.1250
1 ∕ 16 -64
3 ∕ 64 3 ∕ 64 1 ∕ 16 52 49 49 43 3 ∕ 32 38 32
15 ∕ 32 31 ∕ 64 33 ∕ 64 17 ∕ 32 17 ∕ 32 35 ∕ 64 37 ∕ 64 19 ∕ 32 19 ∕ 32
72
9 ∕ 16 -12
18 27
5 ∕ 64 -60
72
3 ∕ 32 -48
5 ∕ 8 -11
50
12 18 27
7 ∕ 64 -48 1 ∕ 8 -32
40
11 ∕ 16 -11
16
9 ∕ 64 -40 5 ∕ 32 -32
5 ∕ 8
3 ∕ 4 -10
1 ∕ 8 30
21 ∕ 32 43 ∕ 64 11 ∕ 16 23 ∕ 32 23 ∕ 32 49 ∕ 64 51 ∕ 64 13 ∕ 16 53 ∕ 64 27 ∕ 32 53 ∕ 64
36
12 16 27
11 ∕ 64 -32 3 ∕ 16 -24
9 ∕ 64 26
32
22 20 16 12 10
13 ∕ 16 -10
13 ∕ 64 -24 7 ∕ 32 -24
7 ∕ 8 -9
12 14 18 27
32
15 ∕ 64 -24
7 4 3 3
1 ∕ 4 -20
24 27 28 32 20 24 27 32 20 24 27 20 24 27
15 ∕ 16 - 9
1 - 8
7 ∕ 8
12 14 27
59 ∕ 64 15 ∕ 16 31 ∕ 32 63 ∕ 64
7 ∕ 32
F
5 ∕ 16 -18
1 1 ∕ 8 - 7
17 ∕ 64
I J
12
1 3 ∕ 64 1 7 ∕ 64 1 11 ∕ 64
1 1 ∕ 4 - 7
12
9 ∕ 32 5 ∕ 16
3 ∕ 8 -16
1 3 ∕ 8 - 6
1 7 ∕ 32
12
1 19 ∕ 64 1 11 ∕ 32 1 27 ∕ 64 1 29 ∕ 64
21 ∕ 64
Q R U
1 1 ∕ 2 - 6
12
7 ∕ 16 -14
1 5 ∕ 8 - 5 1 ∕ 2
1 3 ∕ 4 - 5 1 7 ∕ 8 - 5 2 - 4 1 ∕ 2
1 9 ∕ 16
25 ∕ 64
X Y
1 11 ∕ 16 1 25 ∕ 32 1 29 ∕ 32 2 1 ∕ 32
1 ∕ 2 -12
2 1 ∕ 8 - 4 1 ∕ 2 2 1 ∕ 4 - 4 1 ∕ 2
27 ∕ 64 27 ∕ 64 29 ∕ 64 29 ∕ 64
13 20
2 3 ∕ 8 - 4 2 1 ∕ 2 - 4
2 1 ∕ 8 2 1 ∕ 4
24 2.2500 a These tap drill diameters allow approximately 75 percent 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 3 will reduce defects caused by tap problems and breakage. 0.4531
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