By Don Geary
Hammerdrills are beasts among tools, often punished by long, brutal run-times. My crew and I took nine of these tough tools–all 1/2-inch models–into the field after shop-testing them. We bored so much cured concrete that my hands are still vibrating.
A hammerdrill is a dual-mode tool that shouldn't be confused with its big brother–the rotary hammer. In twist mode, a hammerdrill functions as a standard 1/2-inch twist drill. In hammer mode, a mechanism rapidly spins against the back of the chuck as the motor twists the bit, which pulverizes and removes hard material as it goes. A rotary hammer's mechanism, on the other hand, delivers blows to the back of the bit as it spins. In either mode, a good hammerdrill will bore a smooth, cylindrical hole.
Definitely find yourself some ear protection before using one of these screamers. I also wear gloves to dampen the tool's numbing vibration and a mask to keep concrete dust out of my lungs. Boring holes in anything is dusty, aggressive work, so these nine tools had to withstand the pressure of being muscled by their two handles and balance well enough so that we could place the bit where we wanted without a helping hand.
We tested the following hammerdrills: Bosch 1194AVSRK, the DeWalt DW515, the Fein 638, the Freud FPD182R, the Hitachi DV20V2, the Makita HP2010N, the Metabo 751, the Milwaukee 5378-20, and the Porter-Cable 7751.
Lots of guys keep hammerdrills as their only 1/2-inch drills because they bore well into wood, concrete, and other types of masonry, so we did some time trials with these materials in our shop. We then moved the tools into the field, where they met up with old concrete walls and floors that needed 1/2-inch holes for anchor bolts, threaded rod, and re-bar. We discovered early on that all the tools had nearly equal power and volume, so our emphasis turned to balance, handle design, and features like switches and chucks. We outfitted each tool with the same type of new bits for each test phase: carbide for masonry, and auger bits for wood.
Balance and Weight. Balance is the first thing you notice when you pick up any tool. The best-balanced hammerdrills are easy to manipulate, and don't require secondary hand movements to adjust the tool or access the trigger. They also let us place the bits on the work and start holes without extra effort. DeWalt's tool has the best balance, followed closely by Metabo. We also liked the feel of the Bosch, Freud, and Porter-Cable models.
Tool weights range from 5 to 6.6 pounds. The heavier tool's additional mass acts as a mild shock absorber. With their padded handles, they're the least punishing to use in hammer mode. The lighter tools are easy to maneuver, however. Since hammerdrills are dual-purpose tools, lighter-weight models serve occasional users very well. We hammer frequently though, so we were biased toward the beefier models' extended-use comfort.
Side Handle. Driving one of these tools takes force, so a side-mounted handle is imperative. All the manufacturers equip their drills with adjustable side handles that must work flawlessly while users bear down. The DeWalt, Metabo, and Fein handles have simple designs that function well: twist the handle loose, adjust it anywhere around the chuck collar for optimum position, twist it tight, and you're set to go.
The other tools' side handles tighten or loosen with thumb knobs near the chuck. Unfortunately, these wing nut-like knobs loosen more than they tighten, and can wobble or come off. Metabo's tool has the best side handle of the batch. It's cushioned, and stores bits up to 5 inches long inside.
Depth Bar. The depth bar is an adjustable stop that integrates with the side handle and runs parallel to the bit. It's useful when you have to drill an accurate or uniform-depth hole in wood or concrete. We found that we didn't need that degree of accuracy and the depth bar restricted 360-degree adjustment of the side handle, so the bars spent most of the time in their boxes. A user who needs a smart adjustment will probably like Freud's easy-to-use push-button device, which locks solidly in place. Metabo and Fein offset their bars so they curve in closer to the bit and streamline the tools.