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Obsolete American wood screw gauges
Guage number |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
Diameter (inches) |
0.056 |
0.069 |
0.082 |
0.096 |
0.109 |
0.122 |
0.135 |
0.149 |
0.162 |
0.175 |
0.188 |
0.201 |
0.215 |
0.228 |
0.241 |
0.255 |
Guage number |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
25 |
26 |
27 |
28 |
29 |
30 |
- |
Diameter (inches) |
0.268 |
0.281 |
0.293 |
0.308 |
0.321 |
0.334 |
0.347 |
0.361 |
0.374 |
0.387 |
0.401 |
0.414 |
0.427 |
0.44 |
0.453 |
- |
| Note: The equation relating the gauge number to the root diameter was |  |
Pilot holes for American wood screws
These dimensions are for standard American wood screws, which are tapered. They are not suitable for screws which are not tapered, such as dry wall screws. All dimensions are in inches. The shank pilot hole is one which will clear the thickest part of the screw body.
Gauge Number |
Body Diameter |
Shank pilot hole |
Pilot hole in softwood |
Pilot hole in hardwood |
0 |
0.060 |
1/16 |
1/64 |
1/32 |
1 |
0.073 |
5/64 |
1/32 |
1/32 |
2 |
0.086 |
3/32 |
1/32 |
3/64 |
3 |
0.099 |
7/64 |
3/64 |
1/16 |
4 |
0.112 |
7/64 |
3/64 |
1/16 |
5 |
0.125 |
1/8 |
1/16 |
5/64 |
6 |
0.138 |
9/64 |
1/16 |
5/64 |
7 |
0.151 |
5/32 |
1/16 |
3/32 |
8 |
0.164 |
11/64 |
5/64 |
3/32 |
9 |
0.177 |
3/16 |
5/64 |
7/64 |
10 |
0.190 |
3/16 |
3/32 |
7/64 |
11 |
0.203 |
13/64 |
3/32 |
1/8 |
12 |
0.216 |
7/32 |
7/64 |
1/8 |
14 |
0.242 |
1/4 |
7/64 |
9/64 |
16 |
0.268 |
17/64 |
9/64 |
5/32 |
18 |
0.294 |
19/64 |
9/64 |
3/16 |
20 |
0.320 |
21/64 |
11/64 |
13/64 |
24 |
0.372 |
3/8 |
3/16 |
7/32 |
