TAP DRILL SIZES FOR FORMING TAPS

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Machine Screw Sizes

75% Thread 70% Thread 65% Thread 60% Thread 55% Thread 50% Thread

Tap
Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size

0   80
1   64
1   72
2   56
2   64 .0536
.0650
.0659
.0769
.0780 1.35mm
1.65mm
1.65mm
1.95mm
5/64 .0540
.0655
.0663
.0774
.0785 1.35mm
1.65mm
–
1.95mm
47 .0545
.0661
.0669
.0781
.0791 –
–
1.7mm
5/64
2.0mm .0549
.0666
.0673
.0787
.0796 54

51
47
2.0mm .0554
.0672
.0679
.0794
.0802 54
51
51
2.0mm
– .0558
.0677
.0683
.0799
.0807 1.mm
51
–
–
2.05mm

3   48
3   56
4   40
4   48
5   40 .0884
.0899
.0993
.1014
.1123 2.25mm
43
2.5mm
38
34 .0890
.0904
.1000
.1020
.1130 43
–
39
38
33 .0898
.0911
.1010
.1028
.1140 43
2.3mm
39
2.6mm
33 .0905
.0917
.1018
.1035
.1148 2.3mm
2.3mm
38
2.6mm
2.9mm .0913
.0924
.1028
.1043
.1158 2.3mm
2.35mm
2.6mm
37
32 .0919
.0929
.1035
.1049
.1165 –
2.35mm
2.6mm
37
32

5   44
6   32
6   40
8   32
8   36 .1134
.1221
.1253
.1481
.1498 33
3.1mm
1/8
3.75mm
25 .1141
.1230
.1260
.1490
.1507 2.9mm
3.1mm
3.2mm
–
3.8mm .1150
.1243
.1270
.1503
.1518 2.9mm
–
3.2mm
25
24 .1157
.1252
.1278
.1512
.1526 –
1/8
3.25mm
3.8mm
24 .1166
.1264
.1288
.1524
.1537 32
3.2mm
30
24
3.9mm .1173
.1274
.1295
.1534
.1546 32
–
30
3.9mm
23

10   24
10   32
12   24
12   28
.1688
.1741
.1948
.1978
–
17
10
5.0mm
.1700
.1750
.1960
.1989
18
–
9
8
.1717
.1763
.1977
.2003
11/64
–
5.0mm
8
.1729
.1772
.1989
.2014
11/64
16
8
7
.1746
.1784
.2006
.2028
.1758
4.5mm
5.1mm
–
–
.1794
.2018
.2039
–
–
7
13/64

Fractional Sizes

75% Thread 70% Thread 65% Thread 60% Thread 55% Thread 50% Thread

Tap
Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size Theor. Hole Size Nearest Drill Size

1/4   20
1/4   28
5/16   18
5/16   24
3/8   16 .2245
.2318
.2842
.2912
.3431 5.7mm
–
7.2mm
7.4mm
11/32 .2260
.2329
.2861
.2927
.3452 –
5.9mm
7.25mm
–
8.75mm .2280
.2343
.2879
.2941
.3474 1
A
7.3mm
M
S .2295
.2354
.2898
.2955
.3495 1
15/64
L
7.5mm
8.9mm .2315
.2368
.2917
.2969
.3516 –
6.0mm
7.4mm
19/64
– .2330
.2379
.2936
.2983
.3537 5.9mm
B
–
7.6mm
9.0mm

3/8   24
7/16   14
7/16   20
1/2   13
1/2   20 .3537
.4011
.4120
.4608
.4745 9.0mm
–
Z
–
– .3552
.4035
.4137
.4634
.4762 9.0mm
Y
10.5mm
–
– .3566
.4059
.4154
.4660
.4779 –
13/32
–
–
– .3580
.4084
.4171
.4686
.4796 T
–
–
15/32
– .3594
.4108
.4188
.4712
.4813 23/64
–
–
12mm
– .3608
.4132
.4205
.4738
.4830 –
Z
–
12mm
31/64

Metric Sizes

Metric Tap Size Tap Drill Size Decimal Equiv. of Tap Drill (Inches) Theoretical Percent of Thread % Probable Mean Oversize (Inches) Probable Hole Size (Inches) Probable Percent of Thread %

M3 x0.5 36
2.7mm
.1065
.1062
86
88
.0026
.0026
.1091
.1088
67
70

M4 x 0.7 27
3.6mm
9/64
.1440
.1417
.1406
72
84
90
.0032
.0032
.0032
.1472
.1449
.1438
54
67
73

M5 x 0.8 14
4.6mm
15
16 .182
.1811
.1800
.177 69
74
79
92 .0035
.0035
.0035
.0035 .1855
.1846
.1835
.1805 53
57
62
76

M6 x 1 7/32
5.4mm
.2188
.2126
65
88
.0038
.0038
.2226
.2164
51
74

M8 x 1.25 7.4mm
L
7.3mm
.291
.290
.2874
71
75
82
.0042
.0042
.0042
.2952
.2942
.2916
59
62
70

M10 x 1.5 U
9.3mm
9.2mm
23/64 .368
.366
.362
.3594 64
69
78
85 .0046
.0046
.0046
.0046 .3726
.3706
.3666
.3640 53
58
67
74

M12 x 1.5 11.3mm
7/16
.4449
.4375
70
86
.0047
.0047
.4496
.4422
57
75

M12 x 1.75 7/16
11mm
.4375
.4331
75
84
.0047
.0047
.4422
.4378
65
73

*Probable percent of full thread produced in tapped hole using standard drill sizes.

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