Superficially, finish nailers can appear almost interchangeable with brad nailers; however, this is not the case. Brad nailers are less costly, but they are less powerful, as well, and therefore entirely unsuitable for working with hardwoods. The choice for most buyers is between gauges: the thickness of the nail the gun is designed to fire.
Nail gauges get smaller as the fastener gets larger, so a 15-gauge nail is thicker than a 16-gauge. With hardwoods, thickness -- and a greater integral resistance to bending -- is not the advantage it may first appear. With densely-grained woods, such as oak, the fastener must be able to deform as it passes through grains of different resistance or brushes up against a knot. A nail that resists deformation can well be left projecting due to an obstacle while a smaller gauge would have slid around and fully penetrated the material. This is a distinct advantage for the 16-gauge over the 15-gauge when it comes to installing hardwood floors.
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A 16-gauge finish nailer is more than adequate to hold down 5/16-inch hardwood, which is the usual thickness of retrofit panels. A 15-gauge may initially appear to have the advantage in that a sturdier nail should logically afford a stronger fastener; but when working with hardwood, there is a unique and important consideration. Particularly dense hardwoods, such as aged Brazilian cherry wood, have a tendency to split. The larger the fastener driven through them, the more likely they are to crack around the head.
For both the aforementioned reasons, if you're considering the purchase of a nail gun solely or primarily for installing hardwood floors, the 16-gauge is recommended. While the 15-gauge guns do usually fire like a cannon, a 16-gauge still recesses the nail heads 1/16- or 1/32-inch through hardwood, which is entirely adequate for a floor installation.
Driving Through Hardwood Floors
Hardwood gets its name from its dense nature. While this is a desirable asset in terms of wear resistance, it makes for a far greater resistance to fasteners. Nail guns that are used for working with hardwood must drive the fasteners far harder than those used with fiberboard. That said, a nail gun that only works with hardwood is a poor investment for most users; it would fire fasteners through softer materials and out through the other side like a bullet. Choose a nail gun that has an adjustable force-of-drive control; 100 pounds per square inch of torque is usually adequate to fasten hardwood floors with 1 1/4-inch nails.
Most nail guns fire fasteners of between 1-1/4 to 2-1/2 inches. At purchase you will need to choose between sequential and contact fastening, along with an angled -- rather than perpendicular -- magazine that allows access to the tightest corners. A relatively recent innovation is an "air duster," a nozzle near the firing head that blows debris away from the target to ensure pinpoint accuracy. Nail guns have a tendency to jam, especially when the driven fastener hits a preexisting nail, so the nose should be easy to remove without tools then easy to clear and reinstall. Weight and ergonomics are a concern, both for long working days on hardwood floors and for overhead projects. Using any type of nailer for hardwood flooring requires a no-mar tip; otherwise, scuff marks could be left on the surface.