Impact Driver Facts and Tips

This motorized impact driver is a unique tool that allows you to drive hundreds of screws with little effort. Photo Credit: Tim Carter

DEAR TIM: I'm crazy about power tools and in the past few years I've really been enamored with the impact drivers. I don't own one, but really want one. Have you used these tools? Are they really that much different than a power drill? What can you use them for? They look like a drill and seem to have the same controls, so I wonder if it's really worth buying one. I've got a birthday around the corner and my wife is looking for ideas. What should I tell her? Andy S., Palo Alto, CA

DEAR ANDY: Tell your wife to get out the credit card or grab some sweet moola from under the mattress and get one! Oh boy are you going to be happy on your birthday. I can clearly remember the first time I used a cordless impact driver tool to drive some 3-inch screws into wood without a pilot hole. WOW! I'm serious, I was absolutely blown away with the performance of the tool.

Impact drivers have been around for years, and if you look at the name of the tool, it should solicit some interest. I say this because of the word "impact". Hand-powered impact drivers are still available today and work by combining the downward force provided by a hammer blow with the simultaneous twisting motion of the tool.

These combined forces can really tighten a screw or bolt or loosen stubborn ones. Although the powered impact driver I own is called an impact driver, the only downward force it gets is from me if I push down on the tool as it's being used. That force is nowhere near as powerful as that given by a hammer strike.

But all that aside, the powered cordless impact drivers are time and money savers. They also save your wrist, hand and fingers from repetitive motions that can lead to physical injury or fatigue that can contribute to injury.

The powered impact drivers differ greatly from the standard power drill that you have in your workshop. If you've ever driven a four-wheel drive vehicle that has three different transfer case settings, or even a regular standard transmission that has a very low first gear, you can start to appreciate how an impact driver differs from a regular drill.

An powered impact driver has different internal gears that deliver much greater torque or power to the tip of the tool as it turns than you get from a standard power drill. Imagine putting a four-wheel drive vehicle in 4W-drive low and giving the vehicle gas. This gearing allows the power from the engine to be concentrated to move a heavy load slowly or go up a steep hill with virtually no effort.

A powered impact driver employs this same mechanical advantage when it works. It needs to concentrate the power of the motor on the head of the fastener and deliver power not speed. A drill is geared just the opposite. Drills tend to spin much faster meaning they don't have great power at low revolutions per minute.

I've used my powered impact driver in so many ways. It will drive hundreds and hundreds of decking screws and not complain. You can use it very effectively when screwing cabinets to a wall. It works to remove uncompromising and uncooperative screws and bolts.

I love to use my cordless impact driver in tight spots. The design of the tool I have is compact and lightweight. It comes with a great LED light that illuminates the place where the tool tip contacts the fastener. This is just perfect for working inside a dark cabinet or up in a joist cavity where you'd struggle to aim a flashlight.

After you get your new cordless impact driver, it's going to become one of your favorite power tools very quickly. Your screwdriver and nutdriver hand tools will soon start to gather dust as you discover how the impact driver does such a magnificent job of installing and removing screws and other fasteners.

I've had a screwgun for years that I favored to drive screws. It's a tool that was primarily designed for the drywall industry as just about any sheetrock hanger has one. They are like a sports car as they drive screws so fast you just can't believe it. Fortunately, the screwgun is equipped with an adjustable clutch so you don't drive a screw too deeply.

But my impact driver tool has caused me to pretty much ignore my screwgun. The impact driver is more like a heavy-duty pickup truck as it can do a great job doing many things. But like new trucks, it's got a soft side to it so it doesn't act like a bully.

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Related Column: Impact Driver Uses

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