Q&A / 

How to Drive Finish Nails into Wood

DEAR TIM: I was helping my boyfriend install some wood trim this weekend and had a disagreement with him. It was about the proper way to hammer finish nails. He's of the opinion you should drive them flush with the wood and then paint over them. I remember my dad using a small tool he tapped with a hammer to drive the nailhead below the surface of the wood. Then he'd put spackle over the nail to hide it. Can you settle the dispute and offer any tips on how to install finish nails professionally? Becky S., Kissimmee FL

DEAR BECKY: Sometimes I don't like playing the part of Solomon when it comes to domestic squabbles. But in this case, I'll jump in feet first since it's a topic I feel I can offer sound advice.

Your boyfriend may want the rustic look, in which case his method will just barely pass. Your dad, in my opinion, taught you the proper and time-tested way to countersink a finish nail. The tool your dad tapped with a hammer is called a nail set.

Nail sets come in different sizes to match up with the head of the finish nail being driven or set. A nail set is a solid piece of tooled steel that has a square or round surface you tap with a hammer. The tip of the nail set tapers so the tip is quite small, usually slightly smaller than the diameter of the head of the finish nail that's being set.

This gas-powered impulse nail driver does a marvelous job of driving finish nails. Photo Credit: Tim Carter

This gas-powered impulse nail driver does a marvelous job of driving finish nails. Photo Credit: Tim Carter

It's important the tip of the nail set tool is smaller than the nail head. You want the smallest hole possible in the wood to fill or disguise. This is especially true if the wood is to be stained and coated with a clear finish. In these situations, you want small holes that can be filled with a wood filler that matches the finished color and grain of the wood.

Using a nail set is not easy. Driving nails in finished wood trim is an art. To develop great skill, you must practice. The common mistakes rookie carpenters or homeowners make are large bruises or "beauty marks" made by a hammer head that strikes the wood. Believe me, I've done this on more than one occasion. These marks are very difficult to repair and hide.

Driving finish nails requires deft hammer blows. The head of the hammer needs to hit the head of the finish nail squarely and the hammer must hit the nail so the head of the nail contacts the center of the hammer.

Drive the nail with authority, but not full hammer blows. Depending on the size and length of the finish nail, you'll discover you may only need 4 to 6 inches of hammer travel to develop enough force to drive the nail. If the nail is driven just one-quarter inch with each hammer blow, that's sufficient. Remember, you can't have the hammer touch the wood.

When the top of the nail head is about 1/4 to 3/8 of an inch away from the surface of the finished wood, stop hitting it with the hammer. It's now time to use the nail set. Place the tip of the nail set in the center of the nail head and tap it lightly with the hammer. The nail may only move 1/16th inch with each hammer blow. This is fine. It's all about precision, not power.

If you don't have the nail set lined up directly with the nail, the nail set will jump off the head of the nail and make a new hole on the side of the finish nail. This is unacceptable if the wood will be stained. If the wood will be painted, you can fill this extra hole with spackling compound.

The trick is to drive the finish nail so the top of its head is about 1/16th inch below the surface of the finished wood. This is not as easy as you might think, and the degree of difficulty depends on the size of the finish nail. Larger finish nails are much harder to countersink than small ones because the larger nails offer more resistance when you're driving them.

If you've never done this before, you should practice using scrap finish lumber. I would create a simulation where you have a couple of piece of framing lumber nailed together. To these, nail a small piece of drywall. Then try to nail a piece of finish trim to this assembly. Drive and countersink at least 25 nails before you advance to a real piece of trim. When you do start to nail real pieces of trim, start in a closet or on baseboard you know will be hidden with furniture. The last thing you should nail is a piece of door or window casing at eye level where the mistakes you make will be visible for all to see.

If you want to avoid the possibility of making a mistake, consider using a powered finish nailer. These tools have been around for decades and they drive and countersink finish nails with the squeeze of a trigger. The tools drive all sizes of finish nails from 2.5 inches long and normal nail diameters down to tiny 1/2-inch long pins. These pin nails are so thin, they look just like a straight pin. They're made to attach small pieces of decorative trim.

The nail guns can be powered by compressed air, electricity or propane. I've used all different types of these finish nail guns and they all work well. I prefer to use the guns that don't require compressed air as the air hoses and air compressors can be a problem to work around.

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