Variable Output

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.

Brushless Motor

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.

Battery Gauge

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.

Belt Hook

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.

LED Light

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.