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Machinist Drill Bit Size Table | Drill Bit Size Chart | ISO Metric Drill Bit Size Table
ANSI and ISO Twist drill size chart Fractional and Metric Sizes per. ANSI/ASME B94.11M- below are the standard size drill bits used and readily available in industry. Fractional sizes are measured in inches, while metric sizes are measured in millimeters. The drill size chart contains twist drill data for up to 1.0 inches in diameter.
For typical mechanical tolerances that are achievable see: Drilling Tolerances Capabilities Chart
ANSI Size Drill Bit Chart
ISO (Metric Size Drills) & Conversion to Inches
Drill
(in.)
Decimal
Drill
(in.)
Decimal
Drill
(in.)
Decimal
Drill
(mm)
Decimal
(in.)
Drill
(mm)
Decimal
(in.)
Drill
(mm)
Decimal
(in.)
80
.
1/8
.
O
.
.35
.
3.4
.
8.0
.
79
.
30
.
P
.
.4
.
3.5
.
8.1
.
1/64
.
29
.
21/64
.
.45
.
3.6
.
8.2
.
78
.
28
.
Q
.
.5
.
3.7
.
8.25
.
77
.
9/64
.
R
.
.55
.
3.75
.
8.3
.
76
.
27
.
11/32
.
.6
.
3.8
.
8.4
.
75
.
26
.
S
.
.65
.
3.9
.
8.5
.
74
.
25
.
T
.
.7
.
4.0
.
8.6
.
73
.
24
.
23/64
.
.75
.
4.1
.
8.7
.
72
.
23
.
U
.
.8
.
4.2
.
8.75
.
71
.
5/32
.
3/8
.
.85
.
4.25
.
8.8
.
70
.
22
.
V
.
.9
.
4.3
.
8.9
.
69
.
21
.
W
.
.95
.
4.4
.
9.0
.
68
.
20
.
25/64
.
1.0
.
4.5
.
9.1
.
1/32
.
19
.
X
.
1.05
.
4.6
.
9.2
.
67
.
18
.
Y
.
1.1
.
4.7
.
9.25
.
66
.
11/64
.
13/32
.
1.15
.
4.75
.
9.35
.
65
.
17
.
Z
.
1.2
.
4.8
.
9.4
.
64
.
16
.
27/64
.
1.25
.
4.9
.
9.5
.
63
.
15
.
7/16
.
1.3
.
5.0
.
9.6
.
62
.
14
.
29/64
.
1.35
.
5.1
.
9.7
.
61
.
13
.
15/32
.
1.4
.
5.2
.
9.75
.
60
.
3/16
.
31/64
.
1.45
.
5.25
.
9.8
.
59
.
12
.
1/2
.
1.5
.
5.3
.
9.9
.
58
.
11
.
33/64
.
1.55
.
5.4
.
10.0
.
57
.
10
.
17/32
.
1.6
.
5.5
.
10.5
.
56
.
9
.
35/64
.
1.65
.
5.6
.
11.0
.
3/64
.
8
.
9/16
.
1.7
.
5.7
.
11.5
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.
55
.
7
.
37/64
.
1.75
.
5.75
.
12.0
.
54
.
13/64
.
19/32
.
1.8
.
5.8
.
12.5
.
53
.
6
.
39/64
.
1.85
.
5.9
.
13.0
.
1/16
.
5
.
5/8
.
1.9
.
6.0
.
13.5
.
52
.
4
.
41/64
.
1.95
.
6.1
.
14.0
.
51
.
3
.
21/32
.
2.0
.
6.2
.
14.5
.
50
.
7/32
.
43/64
.
2.05
.
6.25
.
15.0
.
49
.
2
.
11/16
.
2.1
.
6.3
.
15.5
.
48
.
1
.
45/64
.
2.15
.
6.4
.
16.0
.
5/64
.
A
.
23/32
.
2.2
.
6.5
.
16.5
.
47
.
15/64
.
47/64
.
2.25
.
6.6
.
17.0
.
46
.
B
.
3/4
.
2.3
.
6.7
.
17.5
.
45
.
C
.
49/64
.
2.35
.
6.75
.
18.0
.
44
.
D
.
25/32
.
2.4
.
6.8
.
18.5
.
43
.
E
.
51/64
.
2.45
.
6.9
.
19.0
.
42
.
1/4
.
13/16
.
2.5
.
7.0
.
19.5
.
3/32
.
F
.
53/64
.
2.55
.
7.1
.
20.0
.
41
.
G
.
27/32
.
2.6
.
7.2
.
20.5
.
40
.
17/64
.
55/64
.
2.65
.
7.25
.
21.0
.
39
.
H
.
7/8
.
2.7
.
7.3
.
21.5
.
38
.
I
.
57/64
.
2.75
.
7.4
.
22.0
.
37
.
J
.
29/32
.
2.8
.
7.5
.
22.5
.
36
.
K
.
59/64
.
2.9
.
7.6
.
23.0
.
7/64
.
9/32
.
15/16
.
3.0
.
7.7
.
23.5
.
35
.
L
.
61/64
.
3.1
.
7.75
.
24.0
.
34
.
M
.
31/32
.
3.2
.
7.8
.
24.5
.
33
.
19/64
.
63/64
.
3.25
.
7.9
.
25.0
.
32
.
N
.
1
1.000
3.3
.
31
.
5/16
.
Fractional and Metric Sizes per. ANSI/ASME B94.11M-
Drill Bits, also called Twist drills are available with straight or tapered shanks though the most common drill bits will have straight shanks.
Related:
This chart shows the diameters of letter gauge drills size A (the smallest) to size Z (the largest).
Drill Inch mm A 0.234 5.94 B 0.238 6.05 C 0.242 6.15 D 0.246 6.25 E 0.250 6.35 F 0.257 6.53 G 0.261 6.63 H 0.266 6.76 I 0.272 6.91 J 0.277 7.04 K 0.281 7.14 L 0.29 7.37 M 0.295 7.49 N 0.302 7.67 O 0.316 8.03 P 0.323 8.20 Q 0.332 8.43 R 0.339 8.61 S 0.348 8.84 T 0.358 9.09 U 0.368 9.35 V 0.377 9.58 W 0.386 9.80 X 0.397 10.08 Y 0.404 10.26 Z 0.413 10.49
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