Impact driver 101—the basics
A few years ago, cordless impact drivers were a specialty tool, rare on job sites and scarce on store shelves. Today, you'll see several models at any tool retailer and hear their machine-gun chatter wherever there's construction. When a tool gains popularity that fast, you have to wonder what's going on. And, more important, what you're missing.
To sort out the pros and cons of impact drivers, we put them in the hands of our staff editors and field editors, who are pros on the job and DIY guys at home. Here's what we learned:
Tip 1: It's all about torque
Impact drivers have one overwhelming advantage over standard drills and drivers: enormous torque. Basically, that means you can drive a big screw (or bore a big hole) with a small driver. In this photo, we sank 3/8 x 10-in. self-drilling lag screws into cedar lumber. No pilot holes, no cheating.
Tip 2: Not just for driving screws
Impact drivers make great drills. With small bits (up to 1/4 in. or so), they act like a drill—but at nearly twice the rpm of most cordless drills. With bigger bits, they kick into high-torque impact mode so you can bore a big hole with a small driver.
Tip 3: One-handed driving
With a standard driver, you have to get your weight behind the screw and push hard. Otherwise, the bit will “cam out” and chew up the screw head. Not so with an impact driver. The hammer mechanism that produces torque also creates some forward pressure. That means you don't have to push so hard to avoid cam-out. Great for one-handed, stretch-and-drive situations.
Tip 4: The only driver you'll ever need?
Maybe. An impact driver will handle just about any job, and some of our testers have already retired their old drivers. But when high torque isn't needed, most of us like to avoid the noise and reach for standard cordless drills or drivers instead.
Tip 5: Loud, really loud
An impact driver can bring a heavy-metal drummer to tears. Wear muffs or earplugs—or get fitted for a hearing aid. Your call.
Tip 6: It's not a hammer drill
An impact driver works kind of like a hammer drill and sounds a lot like one. But it's no substitute for a hammer drill. An impact driver's innards are engineered to generate torque, not powerful forward blows.
Tip 7: Use hex shafts only
The chuck on an impact driver makes for quick changes; just slide the collar forward and slip in the bit. But you'll have to buy hex-shaft drill bits. Regular bits won't work.
Tip 8: Small and smaller
Generally, there's a big torque difference between 12- and 18-volt models. But some of the 18-volt sluggers are amazingly compact—not much bigger than their 12-volt cousins. Big torque in a compact tool—that's why most of our testers favored the 18-volt versions.
Driver Size Comparison
The 18-volt driver is only slight larger than the 12-volt driver. Both are compact.
Tip 9: Easy to handle
You might think that extreme torque puts extreme strain on your arm. Nope. For reasons Isaac Newton could explain, an impact driver actually generates less wrist twist than a standard driver. Don't be fooled by the macho-man feeling you get when you effortlessly sink a big screw. A little princess can do the same thing.
Tip 10: Consider a combo kit
For a few bucks more than an impact driver alone, you can add a driver, a drill or a hammer drill to your tool collection. This driver/impact driver twosome cost us just $25 more than either tool sold separately. We couldn't resist.
Tip 11: Prepare for impact
Pick up a set of hex-shaft accessories for about $25 (drill bits, driver bits, socket adapters). You'll want most of that stuff sooner or later, and buying a kit will save you a few bucks. Check the label and get a set that's tough enough for impact-driver duty.
Tip 12: They all look alike outside, but . . .
The difference is how they transfer torque from the motor to the chuck. On a standard drill or driver, the motor and chuck are locked together through gears; as the workload increases, the motor strains. An impact driver behaves the same under light loads. But when resistance increases, a clutch-like mechanism disengages the motor from the chuck for a split second. The motor continues to turn and builds momentum. Then the clutch re-engages with a slam, transferring momentum to the chuck. All of this happens about 50 times per second, and the result is three or four times as much torque from a similar-size tool.
Impact Driver/Standard Driver Comparison
These two tools may look alike on the outside, but they operate differently.
Tip 13: Good for gearheads, too
They don't have nearly the torque of big impact wrenches, but cordless impact drivers can be a time-saver when you tinker with engines. They're perfect for small engines, where less torque is usually enough. For automotive work, consider an “angle” version, such as the Craftsman shown later. Hitachi, Makita, Ridgid and others also make angle impact drivers.
Impact driver round-up and test results
It wasn't easy, but after weeks of testing, retesting and arguing, we settled on six favorites. The models shown here are widely available at home centers and hardware stores. If you're willing to do some hunting, you'll find several other models and manufacturers.
Tip: Watch for falling prices. Don't be surprised if you find lower price tags than listed here. We watched prices during a six-week period and saw prices drop on one out of every four models shown here. The discounts (sometimes sales, sometimes permanent price cuts) were in the 10 to 20 percent range.
Impact driver round-up and test results, continued
Drill Master 67028
Cost: $45 (driver, one battery, charger; each sold separately)
Torque: 850 in.-lbs.
Weight: 4.2 lbs.
Battery: 18V NiCad (1)
Unbelievable price: about half the cost of any other model we tried. Available at harborfreight.com.
Our Over-All Favorite: Milwaukee 2650-22
Cost: $320 (Ouch!)
Torque: 1,400 in.-lbs.
Weight: 3.5 lbs.
Battery: 18V lithium (2)
Of our 10 testers, eight gave this one the top rating. In our lag-screw races, it consistently matched or exceeded the others. In addition to raw power, it has all the features we loved: a tool-belt hook, a bright work light and a battery “fuel gauge.”
Bummer: No onboard bit storage.
Dissenting opinion: The DeWalt
DCF826KL is better. It has almost
as much torque, but it's lighter, more
compact and comfortable.
— Gary Wentz, senior editor
Compact Bargain: Hitachi WH10DFL
Torque: 840 in.-lbs.
Weight: 2.2 lbs.
Battery: 12V lithium (2)
You can find a smaller and lighter driver, or more torque, or a lower price. But for a combination of all three of those traits, you can't beat this light, powerful, affordable little gem.
Cramp warning: If you have big hands or wear gloves on the job, the handle might be too short. Otherwise, it's one of the most comfortable drivers we tested.
Big Power in Small Packages
Torque: 930 in.-lbs.
Weight: 2 lbs.
Battery: 12V lithium (2)
Among the 12-volt models we tried, this one takes two prizes: lightest and most compact. Plus, it's a runner-up in torque.
Bonus points: Battery fuel gauge!
Torque: 950 in.-lbs.
Weight: 2.3 lbs.
Battery: 12V lithium (2)
This driver tops our list for 12-volt torque. And although it's taller than most, it's lightweight and comfy.
Dissenting opinion: Torque—it's THE
reason to have an impact driver. So
these 12-volt models just don't make
sense. Get an 18-volt.
— Max Lemberger, field editor
Terrific Torque, Low Prices
Torque: 1,600 in.-lbs.
Weight: 3.6 lbs.
Battery: 18V lithium (2)
You can't beat this combination: Top-tier torque at a price that's about $100 below most of the competition.
Skepticism: Top torque rating by far, but in our tests it performed about the same as other pro-grade 18-volt models.
Torque: 1,200 in.-lbs.
Weight: 4.5 lbs.
Battery: 18V NiCad (2)
Though not as powerful as most of the other 18-volt models, this driver has plenty of torque for all but the toughest jobs—and a crazy-low price tag.
Curmudgeon's note: I wouldn't buy anything with
a NiCad battery. Lithium is the only way to go.
—Travis Larson, senior editor