Field-Testing

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Panasonic's rubber side handle is the softest and provides a sure grip and some vibration protection.

Credit: Photo: dotfordot.com

The majority of the work that I performed in the field with these rotary hammers consisted of drilling 1/2- or 5/8-inch-diameter holes about 8 inches deep into old concrete for rebar dowels. Other common uses included drilling 4-inch to 6-inch-deep holes for various anchors. All of my drilling was either in a downward or a horizontal direction.

I tested these tools in many different types of concrete; the strengths of each varied as well as the size of the aggregate, both of which can make a measurable difference in drilling performance. To be fair, I used all of the tools at each location, and I used identical bits in each tool. I got a good feel for the performance characteristics and preferred features of these rotary hammers as I used them on the job.

Depth Stops. All the tools except the Metabo have an adjustable stop rod attached at the side handle. To adjust the depth of drilling, these handles must be loosened to slide the rod forward and back and then retightened before drilling. The first problem with this setup on a lot of the models is that the handle can be easily moved out of your favored position while you're setting the depth stop, except for on the Makita, which has grooves to hold the handle in place. The second problem is that the smooth rods can slide through their clamps when pressure is applied. A better design on the Bosch and Milwaukee models eliminates both of these problems: Press a separate thumb lever on the side handle to engage and disengage locking teeth on a locking clamp, which provide a positive mechanical lock to the matching toothed rod. This system is fast and easy to use, and keeps the depth-setting function independent of the handle positioning.

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Drill-only and hammerdrilling modes are standard, but some, like the Bosch, have a hammer-only mode.

Credit: Photo: dotfordot.com

Reversing. The forward and reverse buttons on these tools should be easy to activate without loosening your grip on the tool, even while wearing gloves. Most of the buttons in the test group were within easy reach. The Bosch required me to stretch my hand off the grip, and the top-mounted switch of the Metabo felt like it was in the wrong place.

Grips. An important feature of a rotary hammer is the rear handle and trigger assembly. A good tool should be comfortable to hold and operate, even while wearing thick gloves. One reason for this is because during cold weather, squeezing the grips coupled with the vibration of the hammer causes the operator's fingers to get colder much faster than normal, so gloves are a necessity. And even in warm weather I often use heavy work gloves during extended use to help isolate vibration and reduce fatigue.

The ideal tool has a large rear-handle opening with plenty of room for gloved fingers and a trigger that is big enough to accept two fingers. It should also have grippy material on the rear and side handles.

Both Hilti models, the Bosch, and the Makita meet these criteria. The Metabo features a shock-isolated flexible side handle, but its plastic rear handle is too slippery. The Milwaukee has a unique trigger–a long triangular shape that pivots where it enters the handle–that worked well but tended to activate when carried around with a gloved hand. It has non-slip coverings on the rear handle but not on the hard-plastic side handle. The Panasonic has plenty of room and non-slip grips, but only a one-finger trigger. Both DeWalts have decent rear grip surfaces, but slippery, hard-plastic side handles and only single-finger triggers. A heavy glove may be a bit cramped in the smaller rear handle of the 18-volt tool.

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Depth-stop adjustment that can be done without loosening the side handle, like on the Milwaukee, was preferred.

Credit: Photo: dotfordot.com

Weight and Balance. As I used each model and developed an understanding of its feel, I didn't give too much consideration to balance because these are two-handed tools, and once I had them in both hands their balance wasn't much of an issue, especially because they're used in many different positions. I also was not very concerned about weight; in fact, a heavier rotary hammer is an advantage in downward work as you let the weight of the tool do most of the work.

That said, one tool did stand out from the rest when I initially picked it up with one hand: The 18-volt DeWalt is just light and balanced enough that you could almost operate it with one hand.

Vibration and Noise. An important contributing factor of worker fatigue is vibration. The three rotary hammers that vibrated the most were (in order) the Bosch, the Milwaukee, and the Panasonic. I felt medium vibration with both Hiltis. The rest were all relatively low in vibration with the Metabo having the least.

The DeWalt tools were helped by a spring-loaded body suspension system the company calls "Shocks" that isolates the user's hands from most of the transmitted impact as long as the spring is not bottomed-out. This system also provides feedback to the user to regulate how hard to push during drilling or even chiseling. As long as the tool is in the middle of the spring travel, the pressure is correct and the vibration is greatly reduced.

Another fatigue factor is noise, both for the operator and for nearby workers. By my observations, both the Bosch and Milwaukee produced the loudest noise; the Makita wasn't as loud, but it had a higher pitch that was just about as annoying. The Hilti and DeWalt models and the Panasonic were the next level quieter. The Metabo was the quietest.