{"id":309,"date":"2024-09-17T18:07:52","date_gmt":"2024-09-17T18:07:52","guid":{"rendered":"https:\/\/leech.caltech.edu\/wp\/?page_id=309"},"modified":"2024-09-19T20:20:00","modified_gmt":"2024-09-19T20:20:00","slug":"american-drill-gauge","status":"publish","type":"page","link":"https:\/\/leech.caltech.edu\/cntl\/?page_id=309","title":{"rendered":"American drill gauge"},"content":{"rendered":"\n
\n
<\/div>\n<\/div>\n\n\n\n

There are three systems for designating drill diameters. Small drills use a numerical gauge (larger numbers correspond to smaller diameters). Larger drills use letters (\u201cA\u201d corresponding to the smallest diameter, \u201cZ\u201d to the largest). Drill diameters specified as a fraction of an inch are also common.<\/p>\n\n\n\n

Drill #<\/th>Diameter (inch)<\/th>Diameter (mm)<\/th><\/tr><\/thead>
80<\/td>0.0135<\/td>0.34<\/td><\/tr>
79<\/td>0.0145<\/td>0.37<\/td><\/tr>
78<\/td>0.016<\/td>0.41<\/td><\/tr>
77<\/td>0.018<\/td>0.46<\/td><\/tr>
76<\/td>0.020<\/td>0.51<\/td><\/tr>
75<\/td>0.021<\/td>0.53<\/td><\/tr>
74<\/td>0.0225<\/td>0.57<\/td><\/tr>
73<\/td>0.024<\/td>0.61<\/td><\/tr>
72<\/td>0.025<\/td>0.64<\/td><\/tr>
71<\/td>0.026<\/td>0.66<\/td><\/tr>
70<\/td>0.028<\/td>0.71<\/td><\/tr>
69<\/td>0.029<\/td>0.74<\/td><\/tr>
68<\/td>0.031<\/td>0.79<\/td><\/tr>
67<\/td>0.032<\/td>0.81<\/td><\/tr>
66<\/td>0.033<\/td>0.84<\/td><\/tr>
65<\/td>0.035<\/td>0.89<\/td><\/tr>
64<\/td>0.036<\/td>0.91<\/td><\/tr>
63<\/td>0.037<\/td>0.94<\/td><\/tr>
62<\/td>0.038<\/td>0.97<\/td><\/tr>
61<\/td>0.039<\/td>0.99<\/td><\/tr>
60<\/td>0.040<\/td>1.02<\/td><\/tr>
59<\/td>0.041<\/td>1.04<\/td><\/tr>
58<\/td>0.042<\/td>1.07<\/td><\/tr>
57<\/td>0.043<\/td>1.09<\/td><\/tr>
56<\/td>0.0465<\/td>1.18<\/td><\/tr>
55<\/td>0.052<\/td>1.32<\/td><\/tr>
54<\/td>0.055<\/td>1.40<\/td><\/tr>
53<\/td>0.0595<\/td>1.51<\/td><\/tr>
52<\/td>0.0635<\/td>1.61<\/td><\/tr>
51<\/td>0.067<\/td>1.70<\/td><\/tr>
50<\/td>0.070<\/td>1.78<\/td><\/tr>
49<\/td>0.073<\/td>1.85<\/td><\/tr>
48<\/td>0.076<\/td>1.93<\/td><\/tr>
47<\/td>0.0785<\/td>1.99<\/td><\/tr>
46<\/td>0.081<\/td>2.06<\/td><\/tr>
45<\/td>0.082<\/td>2.08<\/td><\/tr>
44<\/td>0.086<\/td>2.18<\/td><\/tr>
43<\/td>0.089<\/td>2.26<\/td><\/tr>
42<\/td>0.0935<\/td>2.37<\/td><\/tr>
41<\/td>0.096<\/td>2.44<\/td><\/tr>
40<\/td>0.098<\/td>2.49<\/td><\/tr>
39<\/td>0.0995<\/td>2.53<\/td><\/tr>
38<\/td>0.1015<\/td>2.58<\/td><\/tr>
37<\/td>0.104<\/td>2.64<\/td><\/tr>
36<\/td>0.1065<\/td>2.71<\/td><\/tr>
35<\/td>0.11<\/td>2.79<\/td><\/tr>
34<\/td>0.111<\/td>2.82<\/td><\/tr>
33<\/td>0.113<\/td>2.87<\/td><\/tr>
32<\/td>0.116<\/td>2.95<\/td><\/tr>
31<\/td>0.120<\/td>3.05<\/td><\/tr>
30<\/td>0.1285<\/td>3.26<\/td><\/tr>
29<\/td>0.136<\/td>3.45<\/td><\/tr>
28<\/td>0.14<\/td>3.56<\/td><\/tr>
27<\/td>0.144<\/td>3.66<\/td><\/tr>
26<\/td>0.147<\/td>3.73<\/td><\/tr>
25<\/td>0.150<\/td>3.81<\/td><\/tr>
24<\/td>0.152<\/td>3.86<\/td><\/tr>
23<\/td>0.154<\/td>3.91<\/td><\/tr>
22<\/td>0.157<\/td>3.99<\/td><\/tr>
21<\/td>0.159<\/td>4.04<\/td><\/tr>
20<\/td>0.161<\/td>4.09<\/td><\/tr>
19<\/td>0.166<\/td>4.22<\/td><\/tr>
18<\/td>0.170<\/td>4.32<\/td><\/tr>
17<\/td>0.173<\/td>4.39<\/td><\/tr>
16<\/td>0.177<\/td>4.50<\/td><\/tr>
15<\/td>0.18<\/td>4.57<\/td><\/tr>
14<\/td>0.182<\/td>4.62<\/td><\/tr>
13<\/td>0.185<\/td>4.70<\/td><\/tr>
12<\/td>0.189<\/td>4.80<\/td><\/tr>
11<\/td>0.191<\/td>4.85<\/td><\/tr>
10<\/td>0.193<\/td>4.90<\/td><\/tr>
9<\/td>0.196<\/td>4.98<\/td><\/tr>
8<\/td>0.199<\/td>5.05<\/td><\/tr>
7<\/td>0.201<\/td>5.11<\/td><\/tr>
6<\/td>0.204<\/td>5.18<\/td><\/tr>
5<\/td>0.205<\/td>5.21<\/td><\/tr>
4<\/td>0.209<\/td>5.31<\/td><\/tr>
3<\/td>0.213<\/td>5.41<\/td><\/tr>
2<\/td>0.221<\/td>5.61<\/td><\/tr>
1<\/td>0.228<\/td>5.79<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Letter drill<\/th>Diameter (inch)<\/th>Diameter (mm)<\/th><\/tr><\/thead>
A<\/td>0.234<\/td>5.94<\/td><\/tr>
B<\/td>0.238<\/td>6.05<\/td><\/tr>
C<\/td>0.242<\/td>6.15<\/td><\/tr>
D<\/td>0.246<\/td>6.25<\/td><\/tr>
E<\/td>0.250<\/td>6.35<\/td><\/tr>
F<\/td>0.257<\/td>6.53<\/td><\/tr>
G<\/td>0.261<\/td>6.63<\/td><\/tr>
H<\/td>0.266<\/td>6.76<\/td><\/tr>
I<\/td>0.272<\/td>6.91<\/td><\/tr>
J<\/td>0.277<\/td>7.04<\/td><\/tr>
K<\/td>0.281<\/td>7.14<\/td><\/tr>
L<\/td>0.29<\/td>7.37<\/td><\/tr>
M<\/td>0.295<\/td>7.49<\/td><\/tr>
N<\/td>0.302<\/td>7.67<\/td><\/tr>
O<\/td>0.316<\/td>8.03<\/td><\/tr>
P<\/td>0.323<\/td>8.20<\/td><\/tr>
Q<\/td>0.332<\/td>8.43<\/td><\/tr>
R<\/td>0.339<\/td>8.61<\/td><\/tr>
S<\/td>0.348<\/td>8.84<\/td><\/tr>
T<\/td>0.358<\/td>9.09<\/td><\/tr>
U<\/td>0.368<\/td>9.35<\/td><\/tr>
V<\/td>0.377<\/td>9.58<\/td><\/tr>
W<\/td>0.386<\/td>9.80<\/td><\/tr>
X<\/td>0.397<\/td>10.08<\/td><\/tr>
Y<\/td>0.404<\/td>10.26<\/td><\/tr>
Z<\/td>0.413<\/td>10.49<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Source: https:\/\/littlemachineshop.com\/reference\/numberdrillsize.php<\/a> and https:\/\/littlemachineshop.com\/reference\/letterdrillsize.php<\/a>.<\/p>\n\n\n\n

Even smaller drills do exist. See, for instance the table at https:\/\/www.custompartnet.com\/drill-size-chart<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

There are three systems for designating drill diameters. Small drills use a numerical gauge (larger numbers correspond to smaller diameters). Larger drills use letters (\u201cA\u201d corresponding to the smallest diameter, \u201cZ\u201d to the largest). Drill diameters specified as a fraction of an inch are also common. Drill # Diameter (inch) Diameter (mm) 80 0.0135 0.34 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-309","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=\/wp\/v2\/pages\/309"}],"collection":[{"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=309"}],"version-history":[{"count":2,"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=\/wp\/v2\/pages\/309\/revisions"}],"predecessor-version":[{"id":515,"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=\/wp\/v2\/pages\/309\/revisions\/515"}],"wp:attachment":[{"href":"https:\/\/leech.caltech.edu\/cntl\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=309"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}