Nails and Spikes - Withdrawal Force
Allowable withdrawal load or force for a common nail or spike driven into side grain perpendicular to the fibers of seasoned wood (or wet unseasoned wood) can be estimated as
F = 1380 SG5/2 D (1)
where
F = allowable withdrawal load or force per inch of penetration (lb/in)
SG = specific gravity of oven dry wood
D = diameter of nail or spike (inches)
Note that the allowable load is 1/5 of the ultimate withdrawal resistance (USDA document FPL-0100).
Example - Nail Withdrawal Load
The specific gravity of Canadian Spruce is 0.45. The diameter of 20D nail is 0.203 inches. The allowable withdrawal force per inch of penetration can be estimated as
F = 1380 (0.45)5/2 (0.203 in)
= 38 lb/in (lb per inch penetration)
Nail Withdrawal Force Calculator
Imperial Units
Metric Units
Allowable Withdrawal Forces for some Common US Wire Nails
- for Spruce with specific gravity 0.5
| Size | Length (in) | Allowable Withdrawal Force (lb) |
|---|---|---|
| 2d | 1 | 17.6 |
| 3d | 1¼ | 25.3 |
| 4d | 1½ | 39.9 |
| 5d | 1¾ | 46.5 |
| 6d | 2 | 58.5 |
| 8d | 2½ | 81.7 |
| 10d | 3 | 108 |
| 12d | 3¼ | 117 |
| 16d | 3½ | 141 |
| 20d | 4 | 198 |
| 30d | 4½ | 242 |
| 40d | 5 | 290 |
| 60d | 6 | 348 |
Allowable Withdrawal Forces for some Common Metric Wire Nails
- for Spruce with specific gravity 0.5
| Length (mm) | Diameter (mm) | Allowable Withdrawal Force (N) |
|---|---|---|
| 20 | 1.2 | 40.4 (4.12 kg) |
| 25 | 1.4 | 58.9 (6 kg) |
| 30 | 1.6 | 80.8 (8.23 kg) |
| 35 | 1.6 | 94.2 (9.61 kg) |
| 35 | 1.8 | 106 (10.8 kg) |
| 40 | 2.0 | 135 (13.7 kg) |
| 45 | 2.2 | 167 (17 kg) |
| 50 | 2.2 | 185 (18.9 kg) |
| 55 | 2.2 | 204 (20.8 kg) |
| 55 | 2.5 | 231 (23.6 kg) |
| 60 | 2.5 | 252 (25.7 kg) |
| 60 | 2.8 | 283 (28.8 kg) |
| 65 | 2.8 | 306 (31.2 kg) |
| 65 | 3.1 | 339 (34.6 kg) |
| 70 | 3.1 | 365 (37.2 kg) |
| 80 | 3.1 | 417 (42.5 kg) |
| 80 | 3.4 | 458 (46.7 kg) |
| 90 | 3.4 | 515 (52.5 kg) |
| 90 | 3.8 | 575 (58.7 kg) |
| 100 | 3.8 | 639 (65.2 kg) |
| 100 | 4.2 | 707 (72 kg) |
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