Fasten faster

Cordless impact drivers and wrenches are redefining fastening on jobsites. They are lighter, smaller and easier on the user than conventional cordless drill/drivers.

If you think a cordless drill/driver is the ticket for installing fasteners, take a look at the cordless impact drivers and wrenches. They can drive faster, are lighter and smaller than cordless drill/drivers and are easier on the user, say industry experts.

Cordless tool manufacturers have introduced several new models in the past 12 months. However, cordless impact drivers and wrenches have been around for 20 years, says Doug Bock, national sales manager at Panasonic. “The technology is not exotic. It’s a mechanical system that offers high turning torque and high speed that’s ideal for fastening, especially self-tapping screws,” he says.

In Japan and other countries, cordless impact wrenches and drivers have long been the tools of choice for fastening jobs, says Vince Caito, marketing communications manager at Makita. “They have become very popular on the West Coast with garage door installers and are spreading to any job where there is repetitive fastening,” he says.

How and where they work
The impact drivers and wrenches use a spring-loaded mechanism that concentrates turning power, or torque, from the motor into a driving force that turns screws into the work piece or quickly tightens fasteners.

“When resistance is great enough, the spring-loaded mechanism strikes the anvil, exerting tremendous turning force on the fastener and efficiently drives the fastener home,” explains Bock.

“An impact wrench or driver can deliver around 1,550 in.-lbs. of torque, where a typical cordless drill/driver will deliver 450 in.-lbs. They deliver that power with little or no kickback to the user,” says Shane Moll, DeWalt assistant product manager for cordless tools. “They weigh less than most cordless drill/drivers and are up to 35 percent smaller in size. We get the most interest from contractors when they actually see what these tools can drive. They find it amazing to see such a small tool easily drive large lag screws.”

Most of the impact tools are one of two types: an impact wrench or impact driver. However, Panasonic’s Multi-Tool is a hybrid tool that easily converts between an impact driver, wrench or drill.

The impact wrenches have a square drive that use sockets to fasten nuts and bolts or to drive lag screws. Depending on the unit, the square drives are available in 3/8", 1/2" or 3/4" drives. Some units have a hex adapter available so they can be used with smaller sockets, screwdriver tips or drill bits that have hex ends. However, any socket used with these tools should be impact-grade quality. Hand sockets are not built to take the extreme impacts these tools dish out.

Where to use them
Moll says DeWalt researchers and salespeople have seen great interest in these units among garage door installers who want the torque to drive lag screws, HVAC contractors who want the speed to drive self-tapping screws and sprinkler/fire protection contractors who benefit from less kickback when they repeatedly assemble mechanical couplings. “General and concrete contractors find them handy for tightening forms and sinking anchors; carpenters and light-gauge steel framers use the units because they are faster for fastening and can get into tight spaces. Even though they can be used for drilling, contractors still use conventional corded or cordless drills for those tasks,” he says.

Users report these tools offer greater user control and comfort when compared with a cordless drill/driver. “As you use them, they give better feedback to the user about what’s happening with the fastener than a cordless drill/driver. With the variable speed, its easy to get a feel for the fastener,” says Caito.

“You will find the units in the 12- and 14.4-volt range very good at repetitive fastening in wood, concrete and steel work, but don’t count on them for heavy lug nut work,” says Dale Thums, McCulloch Power Tools. “Wood­workers doing repetitive wood screwing really like these units.”

Click here to see impact driver/wrench specs

“The best way to judge what these tools can do is to look at the rotational impact these tools offer,” says Caito. “The higher voltage units have more power. You’ll find that a 12-volt unit can easily drive a 3/8" x 4" lag screw, but it will take longer to do it than with a higher-voltage unit.”

While the 9.6- to 14.4-volt units have adequate drilling power for most fastening or concrete anchoring applications, the higher-voltage units definitely have their place. DeWalt, for example, is introducing an 18-volt unit. “While the lower-voltage units are popular, many contractors wanted an 18-volt unit that matches the battery packs they already have,” says Moll.

These tools will typically drive hundreds of fasteners between battery charges. Like their drill/driver counterparts, the battery’s amp-hour rating is a rough indicator of the amount of work the unit can perform between charges.

“Having an extra battery in the charger and swapping them out will keep you running,” says Thums.

Big tools for big jobs
Most of the 18-volt and 24-volt units are built for the big jobs and are finding interesting niches in heavy-duty trades. For example, power line construction workers at We Energies, a Midwest utility, put Milwaukee’s 18-volt impact driver to the test. In the past, crews used gas-powered drills to make holes in poles and drove lag screws by hand.

“The 18-volt drivers with a 7/8" hex drive were lighter, easier to use, more versatile and an all-around better choice than gas-powered drills and conventional wrenches,” says Gary Compton, impact tool product manager at Milwaukee Electric Tool.

The tools are at the top of the cordless impact driver range, producing 3,240 in.-lbs. of torque. “They can turn the head off of a smaller fastener, but are popular with concrete workers assembling forms, tilt-up concrete contractors assembling walls and in maintenance jobs where power is not readily available,” Compton says.

The higher-voltage units work well on large, tight fasteners. “The California Highway Patrol likes the 24-volt units for emergency road service. They have the power to loosen stubborn lug nuts quickly,” Makita’s Caito says.

Pluses and minuses
Every tool has its positives and negatives, and the impact tools are no exception. The experts point out their pluses and minuses:

Plus: The units are more comfortable to use than drill/drivers. The units put the majority of their power into a driving rotational force that’s transmitted directly to the fastener, not to the user’s arms. Even as fasteners tighten, users get little torque reaction transmitted to their hands and wrists.

“A drill/driver will transfer that power back to the user until the clutch slips. Impact tools direct that force onto the fastener. Like any power tool, two hands should be used to control the tool, but these impact tools transmit so little force back to the user that he or she can comfortably operate the unit with one hand,” says Moll.

Minus: The units are noisy. “A common misconception is that the impact noise is the same as a clutch in a drill, and the unit is slipping as it drives the fastener,” says Moll. That sound is the impact mechanism working, not slipping.

Because the units are noisy, hearing protection may be a good idea when used in highly repetitive fastening applications in enclosed areas.

Plus: Impact tools will continue to tighten for as long as you dwell on the fastener. To assure you are not over- or under-tightening, Compton recommends running a fastener down with an impact tool, then using a torque wrench to check it. Adjust the dwell time to best match the desired torque.

Minus: Not for large-hole or highly repetitive drilling. Although these tools can drill holes, the experts say that extensive drilling applications should be done with a conventional drill. Finally, hole saws and impact tools simply do not work well together. “Anything greater than 1 1/2" in diameter will likely bind,” says Bock.

Published in the September/October 2003 issue of Contractor Tools and Supplies magazine.

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