Cordless impact drivers

Impact drivers are ideal for big assembly tasks

Cordless impact drivers make it easier to drive screws with minimal strain on the hand and wrist, so they're ideal for big construction jobs or furniture assembly. They're torquier than regular drill/drivers, and can often sink screws and even lag bolts without a pilot hole (they have less of a tendency to slip out of the screw or bolt head). When the tool senses resistance, an internal hammer gear initiates an impact motion, and torque increases dramatically with no extra effort required on the part of the user.

The main drawback is noise; ear protection is required. Also, while most impact drivers can drill pilot holes, they're much slower at this than regular cordless drills. The extra torque increases the risk of stripping screw heads, but the best impact drivers have speed ranges plus superior trigger control.

Most impact drivers use a quarter-inch hex chuck that accepts both drilling and screw-driving bits with hex shanks. Bits slip in and out quickly, so if you do need a pilot hole you can switch bits instantly. If you prefer a regular chuck, attachments are available (*Est. $30). Although cordless impact drivers are so efficient at their tasks that they don't need much voltage, Fine Homebuilding finds that vibration can cause discomfort in models weighing under 3 pounds.

For brief fastening tasks such as assembling one or two pieces of pre-fabricated furniture, a regular subcompact drill/driver will usually get the job done just fine. For driving small screws, see our separate report on cordless screwdrivers.

Full-size cordless impact drivers

Recent comparison tests say the 18-volt Makita BTD144 (*Est. $335) is the best impact driver currently available, outperforming the 14.4-volt Panasonic EY7540LN2L (*Est. $310) on several points. The Makita impact driver is more expensive, but earns rave reviews for its combination of extra power, compact size, superior conveniences and warranty coverage.

Both these impact drivers hit the "sweet spot" for weight at slightly over 3 pounds. This minimizes vibration without making them tiring to use all day. Both provide three speed ranges and excellent variable-speed triggers. Reviewers say both these cordless impact drivers drive fasteners of all sizes with finesse. The 18-volt Makita provides more power in a more compact 5.5-inch size, however.

Both drivers earn praise in professional reviews at Fine Homebuilding and Fine Woodworking, but the newer Makita BTD144 is also named one of the best tools of the year by both Popular Woodworking and Wood magazines. The latest comparison tests at Popular Mechanics and the Journal of Light Construction put the Makita BTD144 at the top as well. Tools of the Trade finds the Panasonic a bit large and notes that the direction switch is easy to change accidentally.

Makita's three-year warranty gives the BTD144 another edge. The Panasonic carries only one-year coverage, and we found some complaints at Amazon.com about the EY7540LN2L's durability. The Makita BTD144 impact driver earns a lot of praise there from users, not only for sinking big screws "almost instantaneously" but also for little conveniences like the light that stays on a few seconds after the trigger is released so you can check your work. Owners also like the way the battery light flashes to warn that it's almost time for a recharge.

If low price matters more than weight, vibration, power and runtime, the 18-volt Ryobi P230 impact driver (*Est. $70 without batteries) performs reasonably well in tests and gets mostly high ratings from over 50 users at HomeDepot.com. You can use it with Ryobi 18-volt Li-ion (*Est. $100) or Ni-Cd (*Est. $60) batteries, sold separately.

Subcompact impact drivers

If you only plan to drive a lot of small fasteners, consider a subcompact Li-ion impact driver. Most reviewers like their light weight, and find that 10.8 to 12 volts provides enough power for most homeowner jobs. Note that like bigger impact drivers, these little models are still noisy enough to require ear protection.

April 2009 comparison tests at Woodworker's Journal give top ranking to the 10.8-volt Makita TD090DW (*Est. $120), especially for superior trigger speed control. Popular Woodworking also recommends this 2-pound Makita impact driver in a December 2008 review. Amazon.com users express enthusiasm over its combination of power and light weight; one user notes that he was able to drive over 300 three-inch stainless-steel screws without recharging. Another finds it tricky to get a screw started slowly. Note that you can get this driver with a 10.8-volt drill in the Makita LCT203W kit (*Est. $160).

Woodworker's Journal notes that if you have smaller hands, the 10.8-volt Hitachi WH10DL (*Est. $135) might be more comfortable, and like the Makita, itÔs praised by Amazon.com users. The 40-minute charger is a bit faster than the Makita's 50-minute charger, and Hitachi's 10-year warranty is a big plus. However, Woodworker's Journal says the Makita is slightly easier to control.

The 12-volt Li-ion Bosch Impactor PS40-2A (*Est. $140) earns accolades at Fine Woodworking and Tools of the Trade. Unlike most impact drivers, it can't drill holes; it just drives screws. Pilot holes generally aren't needed, however, and the Bosch weighs just 2.2 pounds. This little impact driver has also wins over owners posting at retail sites like Lowes.com and NorthernTool.com. Earlier (circa 2007) Toologics.com tests found the Bosch PS40-2A as powerful as a Bosch hammer drill weighing three times as much.

If you're making furniture and need optimal finesse, reviews recommend the Panasonic EY7202GQW (*Est. $290). In addition to three speeds, it has a unique digital clutch that turns it off once the screw head is flush. This 12-volt model isn't considered a true subcompact because it uses heavier NiMH batteries that give it a weight of 4.1 pounds. The high-capacity 3.5-amp-hour batteries do provide extended runtime for big jobs, though.