Fasten-ating

Cordless impact drivers and wrenches offer serious power in a compact package

by Clair D. Urbain

If you think a cordless drill/driver is the ticket for installing fasteners, take a look at 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 introduced several new models in the past 12 months. However, cordless impact drivers and wrenches have been around for 20 years.

“The technology is not exotic,” says Doug Bock, national sales manager at Panasonic. “It’s a mechanical system that offers high turning torque and high speed that’s ideal for fastening, especially self-tapping screws.”

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 are spreading to any job where there is repetitive fastening,” he says.

How they work
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 workpiece 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,” says Bock.

Shane Moll, assistant product manager for cordless tools at DeWalt, states that an impact wrench or driver can deliver around 1,550 inch-pounds of torque, where a typical cordless drill/driver delivers 450 inch-pounds.

“They deliver that power with little or no kickback to the user,” he says. “They weigh less than most cordless drill/drivers and are up to 35 percent smaller in size. We get the most interest from professionals when they actually see what these tools can drive.”

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

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

Where to use them
Production and maintenance pros 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.

Says Dale Thums of McCulloch Power Tools, “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.”

Caito says the best way to judge what these tools can do is to look at the rotational impact these tools offer.

“The higher-voltage units have more power. A 12-volt unit can easily drive a 3/8-inch x 4-inch lag screw, but it will take longer to do it than with a higher-voltage unit,” he says.

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. Several tool makers, for example, recently introduced 18-volt units.

“While the lower-voltage units are popular, many pros wanted an 18-volt unit that matches the battery packs they already have,” says Moll.

These tools 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.

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

Plus: The units are more comfortable to use than drill/drivers. They 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 transfers 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: Noise. “A 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.

The sound is the impact mechanism working, not slipping. Because of that noise, wear hearing protection.

Plus: Impact tools tighten for as long as you dwell on the fastener. To assure you don’t over-/under-tighten, Compton recommends running a fastener down with an impact tool, then using a torque wrench to check it.

Minus: They are not for large-hole or highly repetitive drilling. Although these tools can drill holes, the experts say you should use a conventional drill for extensive drilling applications.

Also, hole saws and impact tools don’t work well together.

“Anything greater than 1 1/2" in diameter will likely bind,” says Bock.

Impact driver/wrench specs

Clair D. Urbain is the editor of Contractor Tools and Supplies magazine, a sister publication of MRO Today. To learn more, visit www.contractortoolsandsupplies.com.

This article appeared in the February/March 2004 issue of MRO Today magazine. Copyright, 2004.

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