Nails, Screws, Bolts, and Other Fasteners - Carpenter's and Builder's Math, Plans, and Specifications - page 21

Ta ble 1-6 Head Diameters

Head Diameter

Screw Gauge Screw Diameter Flat Round Oval

0 0.060 0.112 0.106 0.112

1 0.073 0.138 0.130 0.138

2 0.086 0.164 0.154 0.164

3 0.099 0.190 0.178 0.190

4 0.112 0.216 0.202 0.216

5 0.125 0.242 0.228 0.242

6 0.138 0.268 0.250 0.268

7 0.151 0.294 0.274 0.294

8 0.164 0.320 0.298 0.320

9 0.177 0.346 0.322 0.346

10 0.190 0.371 0.346 0.371

11 0.203 0.398 0.370 0.398

12 0.216 0.424 0.395 0.424

13 0.229 0.450 0.414 0.450

14 0.242 0.476 0.443 0.476

15 0.255 0.502 0.467 0.502

16 0.268 0.528 0.491 0.528

17 0.282 0.554 0.515 0.554

18 0.394 0.580 0.524 0.580

20 0.321 0.636 0.569 0.636

22 0.347 0.689 0.611 0.689

24 0.374 0.742 0.652 0.742

26 0.400 0.795 0.694 0.795

28 0.426 0.847 0.735 0.847

30 0.453 0.900 0.777 0.900

Strength of Wood Screws
Table 1-7 gives the safe resistance, or safe load (against pulling out),
in pounds per linear inch of wood screws when inserted across the
grain. For screws inserted with the grain, use 60 percent of these
values.
The lateral load at right angles to the screw is much greater than
that of nails. For conservative designing, assume a safe resistance of a
No. 20 gauge screw at double that given for nails of the same length,