Colin's Mechanical Data Page

# Tapping and Clearance Drilling Table
# Equivalent Drill Sizes

Tapping and Clearance Drilling Table
All dimensions are in mm
Screw sizes denoted, for example, 2-64 NF and 4-40 NC, refer to the American National Fine and American National Coarse thread systems.
Screw sizes denoted, for example, M 1.6, refers to the Metric thread system. Dimensions are given in mm.

Screw Size

Pan head

Ordinary Nut

Crinkle Washer

Flat Washer

Tapping Hole Dia.

±		0.05
±		0

Clearance Hole Dia.

±		0.12
±		0

Dia.

Height

Across Flats

Across Corners

Thickness

Outside Dia.

Thickness

Outside Dia.

Thickness

2-64 NF
(0.073)

0.167

0.053

0.187

0.217

0.066

0.211

0.0065

1.80

2.38

4-40 NC
(0.112)

0.219

0.068

0.250

0.289

0.105

0.255

0.0065

0.220

0.018

2.30

3.00

6-32 NC
(0.138)

0.270

0.082

0.312

0.361

0.125

0.305

0.009

0.295

0.018

2.80

3.70

8-32 NC
(0.164)

0.322

0.096

0.344

0.397

0.155

0.345

0.0116

0.365

0.018

3.50

4.40

10-32 NF
(0.190)

0.373

0.110

0.375

0.433

0.167

0.380

0.0132

0.400

0.018

3.90

5.00

M 1.6

3.20

0.96

3.20

3.70

1.30

3.70

0.16

4.00

0.40

1.25

2.00

M 2

4.00

1.20

4.00

4.60

1.60

4.60

0.16

5.00

0.40

1.60

2.35

M 2.5

5.00

1.50

5.00

5.80

2.00

5.80

0.16

6.50

0.60

2.00

2.95

M 3

6.00

1.80

5.50

6.40

2.40

6.40

0.16

7.00

0.60

2.50

3.36

M 4

8.00

2.40

7.00

8.10

3.20

8.10

0.28

9.00

0.90

3.30

4.40

M 5

10.00

3.00

8.00

9.20

4.00

9.20

0.30

10.00

1.10

4.20

5.40

M 6

12.00

3.60

10.00

11.50

5.00

11.50

0.40

12.50

1.80

5.00

6.40

M 8

16.00

4.80

13.00

15.00

6.50

15.00

0.40

17.00

1.80

6.80

8.40

M 10

20.00

6.00

17.00

19.60

8.00

19.60

0.55

21.00

2.2

8.50

10.40

Equivalent Drill Sizes
"Number" and "Letter" drills to Metric, and Metric to Imperial (B.S. 328 Pt. 1 1959)

Numbered Drills

Lettered Drills

Metric Drills with no Imperial Equivalent

Drill No.	Imperial Size (Inches)	Metric Size (mm)
1	0.228	5.80
2	0.221	5.60
3	0.213	5.40
4	0.209	5.30
5	0.2055	5.20
6	0.204	5.20
7	0.201	5.10
8	0.199	5.10
9	0.196	5.00
10	0.1935	4.90
11	0.191	4.90
12	0.189	4.80
13	0.185	4.70
14	0.182	4.60
15	0.180	4.60
16	0.177	4.50
17	0.173	4.40
18	0.1695	4.30
19	0.166	4.20
20	0.161	4.10
21	0.159	4.00
22	0.157	4.00
23	0.154	3.90
24	0.152	3.90
25	0.1495	3.80
26	0.147	3.70
27	0.144	3.70
28	0.1405 (9/64)
29	0.136	3.50
30	0.1285	3.30
31	0.120	3.00
32	0.116	2.95
33	0.113	2.85
34	0.111	2.80
35	0.110	2.80
36	0.1065	2.70
37	0.104	2.65
38	0.1015	2.60
39	0.0995	2.55
40	0.098	2.50
41	0.096	2.45
42	0.0935 (3/32)
43	0.089	2.25

Drill No.	Imperial Size (Inches)	Metric Size (mm)
44	0.086	2.20
45	0.082	2.10
46	0.081	2.05
47	0.0785	2.00
48	0.075	1.95
49	0.073	1.85
50	0.070	1.80
51	0.067	1.70
52	0.0635	1.60
53	0.0595	1.50
54	0.055	1.40
55	0.052	1.30
56	0.0469 (3/64)
57	0.043	1.10
58	0.042	1.05
59	0.041	1.05
60	0.040	1.00
61	0.039	1.00
62	0.038	0.98
63	0.037	0.95
64	0.036	0.92
65	0.035	0.90
66	0.033	0.85
67	0.032	0.82
68	0.031 (1/32)
69	0.0292	0.75
70	0.028	0.70
71	0.026	0.65
72	0.025	0.65
73	0.024	0.60
74	0.0225	0.58
75	0.021	0.52
76	0.020	0.50
77	0.018	0.45
78	0.016	0.40
79	0.0145	0.38
80	0.0135	0.35

Drill No.	Imperial Size (Inches)	Metric Size (mm)
A	0.234 (15/64)
B	0.238	6.00
C	0.242	6.10
D	0.246	6.20
E	0.250 (1/4)
F	0.257	6.50
G	0.261	6.60
H	0.266 (17/64)
	0.2677	6.80
I	0.272	6.90
J	0.277	7.00
	0.2795	7.10
K	0.281 (9/32)
	0.2835	7.20
	0.2874	7.30
L	0.290	7.40
M	0.295	7.50
	0.2992	7.60
N	0.302	7.70
O	0.316	8.00
P	0.323	8.20
Q	0.332	8.40
R	0.339	8.60
S	0.348	8.80
	0.3543	9.00
T	0.358	9.10
U	0.368	9.30
V	0.377 (3/8)
W	0.386	9.80
X	0.397	10.1
Y	0.404	10.3
Z	0.413	10.5

Metric Size (mm)	Imperial Size (Inches)
9.50	0.3740
10.80	0.4250
11.00	0.4331
11.30	0.4449
11.50	0.4528
12.50	0.4921
14.00	0.5512
14.25	0.5610
14.50	0.5709
15.00	0.5906
15.25	0.6004
15.50	0.6102
15.75	0.6201
16.00	0.6299

Data not guaranteed free from error.

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Home page first created: February 1st, 1996