Waiting just long enough to charge the batteries, we took the tools into the field. My crew used them to set hollow-metal jambs, screw down underlayment, do light framing, you name it.
At first, all the carpenters balked at using 18-volt drivers. Few of the finish guys felt they needed a heavier or more powerful impact driver; they were more than satisfied with their 12- and 14.4-volt tools. But the results from the field were telling. The new LI tools outperformed their nicad and NiMH tools big time, with a definite weight advantage. Many of the new 18-volt impacts weigh no more than their older, 14.4-volt non-LI counterparts, making the trade up a no-brainer. The guys in the field gravitated to the lighter models even before we ran the head-to-head tests, so weight was a factor in choosing our favorites. But that wasn't all.
Ergonomics. The most significant difference between these tools is the way they feel in your hand, and that includes their weight, balance, overall size, and grip circumference.
A big part of the comfort level is being able to wrap your hand all the way around the grip. From carpenters with plate-sized hands to carpenters with smaller paws, we found the smaller the driver, the more enjoyable it was to use for everybody. The DeWalt, Hilti, Makita, and Panasonic tools were picked up the fastest. The big guns–Bosch, Craftsman, Milwaukee, Ridgid, and Ryobi–were the least popular on the jobsite.
Belt Hooks. Being on my jobs means climbing ladders, carrying materials, and crawling around cabinets. That's why belt hooks or clips were the next feature the crew wanted. But not every tool has them.
The best belt hooks are adjustable to help balance the tool on your belt, no matter whether you are kneeling or climbing a ladder, and all are reversible. The Panasonic's adjustable hooks are the best, and the Hitachi's hook is similar. But both of these crowd your grip when you hold each one in the left hand.
The pop-up Bosch belt clip is too short to engage securely in a toolbelt; I wouldn't trust it with anyone underneath me. The Makita 141 has a reversible belt clip, but not the 142, although the same clip fits on either tool. The DeWalt also fits an optional clip on either side, but it will not come with the tool until the summer. The rest of the tools don't have belt hooks or clips.
Lights. Every driver has an onboard LED light, which proved to be a big hit with the carpenters. With dark corners and cabinets everywhere on a jobsite, there's nothing more helpful that having good light, especially when you want to seat a screw just right. We found that lights bearing directly on the screw head were best. Two designs work well: a nose light like Hilti's, which has three LEDs encircling the bit holder, and trigger lights located just above the trigger, as found on DeWalt, Makita, Milwaukee, Ridgid, and Ryobi. Lights mounted on the battery housing or bottom of the handle were noticeably less focused and didn't provide enough illumination like those on the Bosch, Craftsman, and the Panasonics. (Panasonic has the brightest lights.) The Hitachi's light is on the tip of the belt hook, which provides aim-able light but only on one side.
Bright white lights are more effective than the amber-colored lights of the Bosch and Hitachi. Everyone appreciated how the Makita lights stay on for 12 seconds, then fade out. This lets you avoid an annoying strobe effect when feathering the trigger in a dark cabinet, and also lets you find a dropped screw without running the motor.
Some of the tools reserve the first part of the trigger pull for their lights, and this was handy for lining up the bit on a screw without spinning it. It also made for a useful impromptu flashlight. The tools with this feature are the Bosch, DeWalt, Hilti, and Makitas. The lights on the Hitachi and Panasonic tools are manually switched and stay on a few minutes after putting the tool down, and Bosch's light can be disabled.
Extra Controls. Impact drivers are notorious for having a steep learning curve. With soft screws–brass and even steel hinge screws–it's easy to shear the heads right off. Hilti, Hitachi, and the Panasonic 7540 try to help with an extra control to lower the driving and impact speed, thus reducing torque. Panasonic has three electronic speed settings, and Hilti has a two-speed electronic switch. The Hitachi has a more primitive speed reduction switch that simply limits how far the trigger can be pulled. Despite the good intentions behind these controls, they didn't see much use on the job. My guys want to keep moving, and they have already learned to feather the trigger for control rather than stopping to push buttons. But dialing down the torque could flatten out the learning curve for others.