By Bill Prudehome
Nails can only be used in fibrous material hence you cannot use a nail to hold anything to metal or plastic. The reason a nail works is that when it penetrates the fibrous material, the fibers bend in the direction of the penetration and literally grip the nail. It takes more force to remove a nail then it does to drive a nail.
Although nails come in hundreds of shapes, in this article we will discuss the two most popular; common and finishing nails.
Common nail, used for rough carpentry as the head always shows. Common nails come in sizes from 1 to 4 inches have a smooth shank and a diamond shaped tip. The longer the nail, the thicker it is and the bigger the head. The rule of thumb is that a nail should be three times longer than the thickness of the item that you are attaching. For general 2 x X lumber use a 3.5 or 4 inch nail. 3.5 inch when nailing side-to-side, 4 inch when nailing to an end grain. When nailing two 2 x X pieces of lumber together use a 3.5 inch nail and angle it so that it does not penetrate the second piece of lumber. Nails that penetrate all the way through a board provide less grip than a nail that is buried within the lumber. If a nail penetrates, the penetrating end should be bent over for two reasons, increase the strength of the joint and safety. An improved rough carpentry spiral nail is now being manufactured which provides greater holding power. The spiral nail is twisted and turns as it penetrates the lumber (similar to a screw). Do not use spiral nails for temporary nailing as they are much more difficult to remove than a smooth shank common nail.
Finishing nail, used for finished carpentry as the head can be conveniently recessed and the material filled so that the head does not show. Finishing nails come in sizes from ½ inch to 3^D>" (the smaller ½ inch to 1^D>" are know as brads). The length rule does not apply to finishing nails, as it is usually necessary to use a nail that is much longer than three times the thickness of the item you are attaching. When using finishing nails in hardwood or near the end of a piece of lumber, such as a trim or molding, it is always wise to drill a hole in the material being attached, as this will avoid splitting the lumber. The hole should be slightly less than the diameter of the nail. The best way to determine the size is to use your drill box. Remove the drills and try to place the nail in the hole that the drill came out of. Use the next size down from the last hole that the nail would slide into. Remember that it is not necessary to grip the material being attached, as the head, even a finishing nail head, will hold the material in place.