I bought my first cordless impact driver at a time when few people had one, so it got a lot of attention whenever I brought it on site. Since then, this type of tool has become so common it would be hard to find a tradesperson who did not immediately recognize its distinctive chattering sound.
Impact drivers drive with more power than comparable drill/drivers and produce less torque reaction – that is, they're less likely to twist against your hand when under load. They're also less likely to strip out the heads of fasteners, because the impacting action keeps the bit engaged. You can use impact drivers to drill holes, but most people use them for driving fasteners.
For this article my crew and I tested 18 lithium-ion impact-driver kits. Some companies sell the same tool in two kits – each with different batteries – and in such cases we tested both versions. We used all the drivers for several months, trading them around so that everybody had experience with each one.
Since I build decks and do remodeling, I mainly drive smaller screws; it would be unusual for me to deplete a lithium-ion battery in the 30 to 60 minutes it takes to charge the spare. In most cases I can work until lunch, swap batteries in and out of the charger, and then work uninterrupted the rest of the day. If the work you are doing is so intense you outpace the charger – say you're driving big lags and bolts in rapid succession – then it makes sense to go for a tool with great runtime or switch to a corded model.
Bosch, DeWalt, Hilti, and Milwaukee offer two battery options per tool: five-cell compact batteries and 10-cell full-size batteries. The compact batteries are smaller and lighter, but the full-size batteries have greater runtime (roughly twice as much). If I had to settle on one type of battery, I'd go with a full-size model, because it would work better with the larger cordless tools (circular saws and recip saws) in that manufacturer's lineup.
We got a pretty good sense of how much work the tools could do per charge by using them in the field. But to put actual numbers on their performance, we also tested the tools in the shop by driving 3-1/2-inch Simpson SDS screws unpiloted into Parallam material until the batteries were depleted. We drove fasteners in groups of 10 so the tools would not overheat, then repeated the test with a new battery.
Since Parallam is very dense, we tested again in Douglas fir with a few of the tools. We found that on average, the impact drivers will drive 25 percent more fasteners in solid lumber than in Parallam. We also measured driving speed, by timing how long it took to sink lags in Parallam material. The results of the runtime and timed driving tests can be found in the tables below.
Most impact drivers have a single output range, but a few of the tools in this test have more than one range of speed and power. These variable-output levels are akin to the high and low speed ranges on drill/drivers and are typically set by pressing a button. If the impact driver is so equipped, the operator can choose between high and low or high, medium, and low settings. Within each setting there's a preset range of torque, speed, and impacts per minute (IPM).
I initially considered this feature a gimmick, but after using it a few times I saw the value of being able to turn the power down. The first time, I was driving some large-diameter slotted screws that came with a flat-screen TV mount. Instead of fighting to keep the bit in the slot while feathering the trigger,
I put the tool in the lowest setting and controlled it that way. Being able to turn the power down while fastening drywall or installing cabinets would be reason enough for me to seek a tool with this feature.
A few of the tools we tested – the Makita LXDT01 and the Panasonic and Hilti models – have brushless motors. These motors are more durable (no brushes to wear out) and more compact than standard motors. They are also more efficient, so all things being equal (such as gears and batteries), cordless tools with brushless motors should have superior runtime. Three of the top four finishers in our runtime test have brushless motors.
There is nothing more frustrating than heading out to do a half-hour of punch work and arriving on site with a dead battery that takes 30 to 60 minutes to charge. To prevent this from happening, Hilti, Metabo, Milwaukee, and Ridgid have equipped their batteries with built-in LED gauges. Makita's batteries do not have gauges, but its LXDT01 impact driver has a warning light that flickers when the battery is down to a 20 percent charge.
For me, a belt hook is an absolute must, so I was surprised to find that some impact drivers come without them. Metabo doesn't make one for its tool, and DeWalt and Hilti sell the belt hook as a separate accessory. It's terribly inconvenient to have to buy the hook as an accessory; I've done it before and ended up paying more for the shipping than I did for the part.
Most belt hooks are formed from flat metal; a few are wire bales. I am fine with all of them – except for the adjustable plastic hook on the Hitachi WH18DL, which is bulky and gets in the way.
Every impact driver we tested has a built-in LED light, usually near the nose of the tool or shining up from just above the battery. Either location is acceptable. The Bosch 26618 and the Hilti have (respectively) three and four lights, spaced evenly around the nose of the tool. This makes for exceptionally bright and even light in the work area. All the lights do the job, but I prefer the ones with the delayed-off feature, which keeps them on for a period of time after the trigger is released. The lights on the Hilti, Makita, Milwaukee, and Ridgid tools have this feature. I don't care for the lights on the Panasonic and the Hitachi WH18DL, because they must be manually activated with a separate switch
Our overall favorite is the Makita LXDT01. It's fast, light, and powerful and has excellent runtime. The grip is very comfortable and the 5.5-inch head length makes it the shortest tool tested.
We also like the Hilti and Milwaukee tools, both of which are available with full-size or compact batteries. The Hilti is fast and has exceptionally good runtime; it placed first in the runtime test and second in the timed driving test. Convenience features include a battery gauge and variable output settings.
The Milwaukee is the brute of the bunch – a fast, powerful tool that torques noticeably when you engage the trigger. It came in first in the timed driving test and third in the runtime test. We like the battery gauge and robust wire-bale belt hook.
Greg DiBernardo owns Fine Home Improvements of Waldwick in Waldwick, N.J.
This driver is available in two different kits – the 25618-01 (with standard batteries) and the 25618-02 (with compact batteries). A well-balanced tool, it has a responsive trigger and a comfortable grip. The single light under the chuck does a good job illuminating the work but does not have a delayed-off function. The well-designed hard plastic case is perfectly sized to fit the tool and accessories without taking up too much space. Both kits are worthy contenders.
Bosch's 26618 is a hybrid – a combination of a two-speed drill and an impact driver. To change between modes, the operator shifts a switch on top of the housing. It's an interesting idea, but try as I might, I am unable to come up with a good reason for a hybrid tool. If I want to drill, I would rather use a drill/driver and a standard bit than have to handle a big, heavy combo tool and keep hex-shank drill bits on hand. I do like the three-LED light on the nose of the tool. ]
These two kits contain the same tool with different battery packs – full-size batteries in the DC827KL and compact ones in the DCF826KL. With either battery, the tool itself is light, compact, and well-balanced. It has a responsive trigger and was among the leaders in terms of driving speed. Since it's compatible with DeWalt's older XRP tower-style packs, it will integrate into the company's existing systems. There are a couple of things we don't like about this impact driver: The belt hook must be purchased separately; and when the batteries are low they cut out immediately instead of fading slowly, so you can't squeeze out a few extra fasteners.
LATE ARRIVAL: DEWALT DCF885
This 20-volt Max series tool arrived too late for us to test. Lighter and more compact than previous DeWalt models, it takes the company's new 18-volt slide-style lithium-ion batteries. Features include a belt hook, a one-handed chuck, and a three-LED light with a 20-second delayed-off function. Shown here with a 1.5 Ah compact battery, it also takes a 3.0 Ah standard battery.
HILTI SID 18-A
The SID 18-A is one of my favorites, a feature-packed tool with exceptional runtime and superior driving speed. With the standard battery, it placed first in our runtime test, and with the compact battery (SID 18-A Compact) it beat all the other tools with compact batteries. With either battery it was among the best performers in our driving-speed test. Features include variable-power output, a battery gauge, one-handed bit loading, and a bright four-LED light surrounding the nose. The belt hook – which we didn't get – is a $9 accessory. This model is scheduled for release in January 2012; we tested a prototype.
This tool is light and comfortable to handle but has a longer head than most other impact drivers. In the field it ran longer than expected for a tool with a compact battery, and in the runtime test it beat all but one of the tools with compact batteries. It placed near the middle of the pack in our timed driving test. For someone on a budget – who isn't already committed to another battery system – it would be a reasonable choice. It comes with a small plastic case that makes efficient use of storage space.
Though one of the longer, heavier tools tested, the WH18DL is reasonably comfortable to handle. It's best for larger hands, because the grip flares at the bottom to accept the thick post of a tower-style battery. Added features include a bit holder and a two-position variable-output switch on the handle. The light is built into a pivoting plastic belt hook and must be manually activated. The durability of this hook is questionable – and unless you go to the trouble to fold it down, it's in the way when you use the tool left-handed. The tool performed in the middle of the pack and has too many odd and awkward quirks for me to recommend it.
The BTD141 is light for a tool with a full-size battery, and very compact. It feels fast and powerful in use and was a solid performer in our runtime test, placing fifth. The light does a good job illuminating the work area and remains on for 10 seconds after the trigger is released. The trigger is very responsive, and you can load bits without pulling the chuck collar. The only thing I don't like about this tool is the blow-molded case, which is large and unnecessarily bulky.
This compact tool is similar to the BTD141 but has slightly less torque output and ships with 1.5 Ah batteries instead of the 3.0 Ah batteries that typically come with Makita tools. It does accept 3.0 Ah batteries, however, and it has the same LED light and charger as Makita's other impact drivers. At less than three pounds, it's the lightest impact driver tested and was our go-to model for low-volume work. It placed near the bottom in our timed driving and runtime tests.
Of all the tools we tested, the LXDT01 is our favorite. It resembles the older BTD141 and uses the same battery, but it has a number of upgraded features, including a brushless motor, variable-power output, a one-handed chuck, and a switch for disabling the light. The tool is fast and has very good runtime; it placed fourth in both the runtime and the timed driving tests. The only thing missing from this tool is a battery gauge, though it does have an indicator lamp that flashes when the charge is down to about 20 percent.
The SSD 18LT is big and powerful, but it's not very comfortable to use. The handle is fatter than most, and no one on the crew liked how it felt. This is the only tool we tested for which there was no belt hook – not even as an accessory; instead, it comes with a lanyard so you can hang it from your wrist. Features include variable output and a very nice battery gauge. Most tools with variable output use multiple LED bars to indicate the setting; this one uses a single blinking light. Unfortunately, the light blinks annoyingly when you activate the trigger. The tool comes with an unnecessarily large plastic case.
The Milwaukee 2650 is available in two different kits, the 2650-22 (with standard batteries) and the 2650-21 (with compact batteries). Fast and powerful in use, it torques over – almost like a wormdrive saw – when you engage the trigger and was the top performer in our timed driving test. It ranked high in the runtime test with either battery. Although it's among the heavier tools tested, it's compact and comfortable to use. We like the four-stage battery gauge but wish the button that activates it were easier to push. The trigger is fairly sensitive, but it can be hard to tame this tool on delicate projects. All in all, the 2650 is a solid-performing impact driver that's well worth considering.
Panasonic is the only tool company that also manufactures battery cells, so it's no surprise that its impact driver has superior runtime: It drove more lags per charge than all but one of the tools tested. This tool has a slim, comfortable grip and is light for a model with full-size batteries. Features include a brushless motor, variable-power output, and a manually operated light. The trigger is responsive and provides better-than-average control. The power output button can be difficult to operate – it's under a sticker and you have to hit the sweet spot. I would prefer that the tool had a conventional trigger-operated light.
Of the tools that come with two batteries, this is the least-expensive model we tested. It's well-balanced and has a comfortable grip but is among the longer and heavier compact models. Although it works well enough, its performance was not impressive: It came in last in both the timed driving and runtime tests. Other than its lower-than-average price, there's nothing much to recommend it.
The R86034K is the most feature-rich compact model we tested; it has a battery gauge, a self-ejecting chuck, and a double-LED light that can be activated two different ways – by squeezing the trigger or by using a switch further down the handle. Though one of the heavier compact tools, it's well-balanced and comfortable to use. I particularly like the charger: The indicator lights are big enough to see from across the room, and the level of charge flashes on the battery as it's charging. The included soft case is very compact but lacks dividers to keep items from banging around inside. The price for this tool seems low until you realize it does not include a spare battery. If you add the $70 cost of a second 1.5 Ah compact battery, it's priced in line with competing models. A 3.0 Ah standard battery is available for $99.