Cordless Impact Drivers vs. Cordless Drills – How Do They Compare?
Although they look like a smaller replica, don’t confuse a cordless impact driver with a standard cordless drill or hammerdrill. The biggest difference is inside. Unlike a cordless drill - which creates continuous in-line torque – a cordless impact driver uses an internal spring-loaded pulsating cam and gear mechanism to create rotational torque. In simple terms, the effect is similar to that of a hammer wrapping on a wrench to loosen a stubborn lug nut, only faster.
Cordless impact drivers work like a typical cordless drill until greater torque is needed, at which point the spring and cam mechanism kicks in, with up to 3,000 blows-per-minute (bpm) to increase the torque by almost triple the amount of a cordless drill (e.g. DeWALT’s12-volt cordless impact driver develops 1,000 in/lbs. of maximum torque compared to 350 for a 12-volt drill). And, unlike a hammerdrill, the bit doesn’t “hammer” in and out while rotating – it maintains contact with the fastener even as the hammering effect occurs inside the tool.
Another significant difference is torque delivery. With a cordless drill, the user must literally hold on to counter the tool’s tendency to spin out of his hands. However, with a cordless impact driver the torque is converted directly to the fastener. You can easily hold the tool using one hand without noticing any reactionary torque. This means you can drive fasteners all day long without the arm fatigue or wrist kickback normally associated with a conventional drill/driver.
Because of their added speed (2,400 rpm vs. 2,000 for cordless drills) cordless impact drivers are excellent at driving Tapcon screws into concrete for electrical service panels, hex-head sheet metal screws for installing duct work and metal roofing, drywall screws, and deck screws. In addition, a cordless impact driver fitted with an impact socket adaptor can drive eight-inch lag bolts into pressure treated lumber with ease. All of these capabilities make impact drivers a logical choice for electricians, deck builders, light gauge steel framers, cabinet installers, HVAC installers, sprinkler fitters, and other tradespeople.
Another benefit is size. Cordless impact tools are compact – the models from DeWALT are about 35% the size of a comparable drill/driver. This makes them ideal for getting into tight places for various tasks, such as the installation of cabinets, duct work or overhead fastening on fire sprinkler systems. The weight of a cordless impact driver is about 3.5 pounds vs. 8.7 pounds for a high-voltage drill/driver - another advantage. The lighter tool is easier to handle if you have hundreds of fasteners to drive in a day, or if you’re doing overhead work.
Cordless impact tools are not as quiet as conventional drill/drivers. The internal mechanism in these tools results in a rapid chatter sound when torque is applied to the fastener. Tough fasteners, however, will be driven significantly quicker. And, as a rule, the battery in a cordless impact driver will last longer between charges, partly because an equal amount of energy is pulled from the battery regardless of the torque required to drive the fastener. With a cordless drill, the higher the torque required, the greater the drain on the battery.
Using a cordless impact driver requires a slightly different technique compared to using a standard drill/driver. Once the fastener starts into the material a light grip is all that’s required to drive it home. Unlike a drill/driver, on which the user must bear down to force the fastener into the material, an impact driver will do most of the work without stripping out the fastener head.
Cordless impact drivers have a quick release chuck that enables split second bit changing. They use a 1/4 inch hex-drive bit system that will accept many accessories, including screwdriver bits, impact socket adaptors for driving lag bolts, and nut drivers for self tapping metal screws. They can also be used for drilling with 1/4 inch hex-shank twist bits in wood or metal drilling, and even spade bits for holes up to about 7/8 inches in diameter for plumbing and electrical wiring. I have found that an impact driver will actually drill holes much faster than a standard drill/driver in most types of material when fitted with the right drill bit.
Cordless Impact Wrenches
The basic difference between cordless impact drivers and cordless impact wrenches is the chuck configuration. Impact drivers have a chuck which accepts 1/4 inch hex-shank bits for screwdriving, drilling, and nut driving. A cordless impact wrench uses a 3/8 inch or a 1/2 inch square anvil primarily for driving impact sockets. In addition, the wrenches develop more torque. Today’s cordless impact wrenches, like the ones from DeWALT, now have enough power to rival many corded electric wrenches, a big plus when you’re up on a lift away from an outlet.
The type of work you’re doing will dictate which category to choose – driver or wrench. For example, if most of your work involves driving self tapping sheet metal screws or deck screws, an impact driver would be right for you. If most of your work involves driving large lag bolts or bolting pipe couplings, a dedicated cordless impact wrench would be a better choice. Although a cordless impact driver can be fitted with a socket adaptor, the larger square shaft of the impact wrench will prove more durable for heavy duty applications.
