In years gone by, nails were the quintessential mechanical fastener in the wood shop. However, as glues have improved and cordless screwdrivers have made using screws a relatively painless procedure, the nail's place in the wood shop has diminished. That being said, there will likely always be a place for nails, brads, and tacks in the woodworker's arsenal, no matter how limited that place may be.
Walk down the fastener aisle of the home center, and you'll find probably a hundred different types and sizes of nails. While most of these are much more conducive for construction purposes, there are a few that you'll want to keep in mind for woodworking projects.
The first thing to consider is the finish of the nail. Most nails have either a bright steel finish or are galvanized to help protect the steel nail from moisture. Be advised that some hardwoods can be stained by the protective coatings applied to the fasteners, so use galvanized nails with caution.
Some nails, such as upholstery tacks, may have a bronze, brass or chrome finish. These are largely decorative nails and should be used in appropriate situations.
Brads are small, thin nails that are typically used for tacking jobs, such as connecting thin plywood to the back of a cabinet. Because of their thin size, they can be a bit temperamental to work with, but are perfectly suited for some jobs.
Recent improvements in pneumatic brad nailers have virtually eliminated the need for hand-nailing of brads, but it's good to keep a box around for situations where you only need a few to perform a tack job.
Finishing nails are a bit thicker than brads and typically come in a wider variety of sizes. They have a head that is only slightly larger than the shank of the nail and are designed to be recessed beneath the surface of the stock with a punch called a nail set.
As with brads, pneumatic finish nail guns have pushed finish nails to the background, as a finish nail gun can insert and recess the nail perfectly at the flick of a switch.
General purpose and finish nails are sized by the term "penny", which dates back to the 1600s. It referred to the cost for a hundred nails of a particular size. For instance, if a hundred nails of a relatively small size cost four pence, they were called "four penny nails" (which is abbreviated as 4d on boxes at your home center). Although the prices have obviously changed, this traditional method of nail sizing is still used in the United States today.
As a general rule, a 4d nail is approximately 1 1/2" in length, where a 16d nail is 3 1/2" long. There are many more sizes available for specialized uses, but the majority will fall into this range.
In most countries, however, the metric system is used to denote nail sizes. For instance, the term 30x2.0 is indicative of a nail that is 30mm in length (not counting the head of the nail) and 2mm in diameter. (Canada uses a modified metric system, in that the nail lengths are listed in inches.)
When using hammer-driven nails in your woodworking projects, particularly finish nails, take care to avoid sinking the nail flush with your hammer.
Doing so may result in an indentation, called a "bruise", caused by the head of the hammer. Instead, stop driving the nail about 1/8" from the stock, and then recess the nail with a nail set.
In the event that your hammer does strike the wood and cause a bruise, immediately soak the bruise with warm water, which will cause the wood to swell and hopefully raise the crushed wood fibers flush with the surface. Let the bruise dry, and then sand it smooth.
Also, keep in mind that when nailing near end grain, a nail is much more likely to cause the wood to split. To avoid this problem, blunt the tip of the nail before driving it into the stock. This will cause the nail to act more like a punch and may prevent the stock from splitting. This method works well for softwoods, but on hardwoods, you may need to drill a small pilot hole to accommodate the nail.