Vibration Isolators. These tools vibrate a lot, impacting with 2,500 to 3,500 blows per minute. Because of this, user fatigue is a concern, especially because it can affect productivity and safety. All of the manufacturers provide cushioned side handles that help absorb the vibrations nicely.
Bosch and Milwaukee go one step further by mounting the trigger grip on rubber isolators with a hinged mount. This feature reminds me of high quality chain saw handles. These isolators noticeably reduce vibration?if you don't push the tool too hard. If you do push too hard, you compress the rubber, minimizing its effectiveness. (Note: Pushing too hard on a rotary hammer slows the tool; back off on the pressure and let the tool do the work.)
Side Handles. A side handle is a must in this category. Not only do you need it to control the tool if it jams, but it also helps maneuver the tool, especially in a horizontal orientation like stripping tile or drilling/chipping straight ahead. Each side handle in the group has a strong, cushioned grip that enables you to hang on in relative comfort. The handle lengths vary from tool to tool. The longer grips provide a bit more leverage and more room to get your hand in the best spot for the task, but they can be awkward in tight spaces. When I took the tools to my crew, we found that handle length boiled down to individual preference with no real performance difference between them.
DeWalt and Metabo take their side handles an ingenious step forward: You can move the handles from just behind the chuck (where you normally find them) to just in front of the trigger grip. This second handle position gets both hands near each other (like on a jackhammer) while drilling or chipping straight down, which makes moving the tool from hole to hole easier and keeps you from having to bend over so far. Switching the Metabo handle is easy and still allows you to reach all of the switches when it's in the upper position. DeWalt's, on the other hand, blocks access to the mode selector switch when mounted near the trigger, which is a small nuisance.
Makita takes a different approach by providing two side handles with their tool: a straight side handle and a D-shaped side handle. The D-handle works exceptionally well for horizontal or overhead drilling/chipping because it's the natural position for your hand during this application; however, Makita doesn't recommend using it while drilling because reaction torque could be an issue: If the tool jams and your hand is stuck inside a D-handle?look out.
Reaction Torque. When drilling in re-bar-embedded concrete, a hammer without torque control or a clutch can be dangerous. Re-bar can stop a drill bit dead in its tracks. The problem: The bit stops while the tool?and your hands?keep going. Thankfully, each tool in the group comes with a torque control clutch to prevent it.
Hilti's torque control is different than the rest of the group. Rather than a mechanical clutch, the tool has an electronic torque sensor called ATC, or Active Torque Control. ATC stops the tool in a split second when it electronically senses torque overload, then requires you to release and re-pull the trigger before the unit will re-start. According to Hilti, ATC stops faster than other clutch systems. Further, other clutch systems allow the bit to start spinning again after a jam if you hold the trigger on. This means the tool can stop and start in a herky-jerky fashion. Of course, despite the hundreds of holes we drilled, we didn't hit any re-bar to get a solid read on either clutch style in the test (I'm sure we'll hit five tomorrow).
Selector Switches. It seems that for machines that do two things?chip and drill?a speed-and-function selector switch should be an easy item to develop, but, since only a few have good switches, apparently it's not. Of all the models in the test, I like the Bosch, Milwaukee, and Makita switches the best. The chip/hammer selector switches all are in good positions, have clear graphics that indicate their function, and they engage easily. For RPM adjustments, these tools use speed dials that work fine. Hilti's switches are good, too, with a speed selector switch that toggles between 50 percent and 100 percent power. The Hilti also has a trigger lock for chipping-only that gives your hand a break from squeezing the trigger.
DeWalt's speed and function switches are decent as well. The Metabo and Hitachi switches were more awkward to use than the others. Hitachi's is hard to reach underneath the tool body while Metabo's switch has inadequate graphics, so it's difficult to know what function you're on. An experienced operator will figure it out fast enough, but I've got enough to think about without having to remember which way to flip the switch.