Withdrawal resistance of nails The withdrawal resistance of a nail indicates its holdi...

Withdrawal resistance of nails

The withdrawal resistance of a nail indicates its holding strength in wood. A formula that is used for bright common nails is where P is the maximum withdrawal resistance (in pounds), S is the specific gravity of the wood at 12% moisture content, R is the radius of the nail (in inches), and D is the depth (in inches) that the nail has penetrated the wood. A 6d (six-penny) bright common nail of length 2 inches and diameter 0.113 inch is driven completely into a piece of Douglas fir. If it requires a maximum force of 380 pounds to remove the nail, approximate the specific gravity of Douglas fir.