Think of a cordless impact driver as a cross between an impact wrench used by auto mechanics and a conventional cordless drill. Though I had heard about these tools, I had never seen anyone using one, so I was skeptical. I drive a lot of screws as a remodeler, and I thought nothing could be faster or more effective than my cordless drill. But when I was given the chance to test several of these tools for JLC, it didn't take me long to realize that a cordless impact driver is a superior tool for running screws. The tool's impact action makes driving 3/8-inch lags feel like you're driving drywall screws, and because impact drivers are about a third smaller than cordless drills, they fit in many places where a drill can't go. Plus, unlike my bulky 18-volt drill, they hang easily from my toolbelt.

Generally, impact drivers are available in the same voltages (9.6 to 18) as cordless drills. To take advantage of the tools' compact size, I limited my test to 12-volt models from DeWalt, Hitachi, and Makita. I also tested 14.4 drivers from DeWalt, Makita, and Milwaukee. Even though these tools are in the middle of the pack in terms of voltage,...

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