What is an impact driver?
An impact driver, as its name says, is a power-packed tool. Designed to drive a screw – a long screw – into even hard woods, it uses a hammering effect to provide far higher torques than even a heavy-duty drill can muster. Another big advantage of an impact driver is that the high torque from the hammering impact is not carried back to the hand that holds the tool.
The tool bit doesn’t require a heavy hand to keep it engaged in the screw head, so there’s almost no chance of “camming out” the screw, damaging the driver bit and destroying the screw head. And it will work where a heavy drill-driver simply cannot be used – even one handed, if necessary.
The other huge advantage of im pact drivers is that they are fast. The shaft turns almost twice as fast as a regular drill, which means driving really long screws – 10 inches and more – takes far less time. And despite its greater torque and speed, the impact driver is lighter than a drill-driver, a big benefit when working overhead or driving a lot of screws on a job.
The only drawback is the noise they make, and the cost, both of which may limit some contractors to using an impact driver. Still, for long term, all-day use, the impact driver pays for itself in productivity. Note that all impact drivers have a hex quick-change chuck so there’s also an investment in the bits, adapters, screwdriver tips needed for the tool. These are special, robust drills and require bits made to sustain the pounding in impact mode.
Impact drivers offer a choice of battery size, type and voltage. In general lithium-ion batttery models are preferable to NiCad because of their improved battery recharging and discharging capabilities. And 18 or 20 volts is better than lower ratings if the driver is going to be used on heavy jobs like driving lag-bolts. For medium sized jobs, a lighter weight 12-volt tool should still perform amazingly well.
If you already have cordless power tools, you’ll probably want to stick with the brand you have since batteries should be interchangeable. You may even be able to buy a bare tool at a lower price and use the batteries and charger you have. Or you may find a kit that has an impact driver and a hammer drill together in a carrying case. That way you get a tool for general construction and one for drilling into concrete and masonry, and you’ll likely save money.
When choosing an impact driver compare the maximum torque the tool develops, the speed of the shaft and whether the tool fits comfortably in your hand. Other features you may like include lighting on the tool, battery conservation switches, tool belt clips and special grips, which increase the versatility, capacity or comfort of the tool. When comparing price, remember to read the specs so that you compare performance as well. And don’t forget to factor in durability. This is a tool that will likely see heavy use.
–by Steve Sturgess