How to Choose Proper Finish Nails

Head and Gauge

• Finish nails are designed to disappear into wood without leaving a noticeable mark. Even though a small hole is inevitable, finish nails have heads that can be round or rectangular and not much bigger than the shaft of the nail. Some finish nail heads have a tiny divot centered on top so you can position a nailset, which is used in conjunction with a hammer to drive the nail below the surface of the wood. Finish nails are usually bright or even shiny metal, with less diameter than any other type of nail. Their gauge -- which is the diameter of the nail -- typically starts at 23 (the smallest) and goes up to 15. Choosing gauge size depends on what type of wood you're nailing, but the most universal gauge is 18, which works for hard or soft wood. Unless the gauge is specified when you purchase the nail, you can't measure the gauge without a pair of calipers. But for all practical purposes concerning gauge, if you find that you're bending nails, use a thicker nail. If you find that you're splitting wood with the nail, use a smaller gauge.

Penetration

• Choose finish nail length according to the thickness of the material that you're nailing through. Most trim molding thicknesses graduate in 1/4-inch increments. Finish nails also graduate in 1/4-inch increments, typically starting at 1 inch and going up to 2 inches long. If you're joining two pieces of wood with equal thickness, choose a finish nail that is 1/4 inch less than the accumulated width of the two pieces. For example, if you are nailing two pieces of 3/4-inch-thick material together, use 1 1/4-inch finish nails. This allows you to set the head of the nail below the surface of the wood without driving it through the face of the adjoining piece. If you're nailing 3/4-inch-thick trim pieces to studs covered by drywall, use 2-inch nails. Sufficient penetration through the top piece of wood or trim should be at least 1/2 inch into the adjoining piece of wood. Anything less than 1/2 inch is typically not enough to hold trim pieces in place.

Brads

• Brads are finish nails that are an inch or less in length. The diameter is smaller than other types of finish nails, and brads typically have a shiny coating or polished appearance. Use brads when nailing materials 1/2-inch-thick or less. Use a pair of diagonal pliers to hold the brad if necessary since it's difficult to hold a brad with your fingers. Brad nail length typically graduates in increments of 1/8 inch starting from 1 inch down to 5/8 inch in length. Brad penetration can be less than 1/2 inch because thinner, lighter material is easier to hold in place, but depending on what you're nailing, brads should penetrate through the wood or trim a minimum of 1/4 inch.

Point

• Finish nails may have different points. Some look like the end of a sharp pencil, while others have a chisel shape. Choose the chisel tip for best results. Round, or pencil tips, can split hardwoods, while the chisel tip -- when properly oriented -- can prevent splitting. Examine the tip of the nail and align the chisel tip parallel with the grain of the wood. The slightly lengthened chisel tip slips between wood fibers and prevents the likelihood of splitting the wood. Chisel-tip nails are found on hand-driven nails as well as air gun nails.

Nail Guns

• Use nail guns whenever possible. Pin nailers work best, and professionals use them regularly to install trim on walls, to build cabinets or carry out other jobs when efficiency is an issue. Pin nailers automatically set the head of the nail -- which is only slightly larger than the shaft -- below the surface of the wood. Pin nails also have an adhesive coating that heats up by friction when the nail is driven into wood. This adhesive helps to bond the nail permanently into the wood. The same principles for length apply to pin nails as hand-driven finish nails, with at least 1/2-inch penetration through the back of the wood or trim required for nails longer than 1 inch. Pin nailers are capable of placing nails in cracks, corners or into profiled moldings where it's impossible to drive nails by hand.