Pistol Grip. Hammerdrills vibrate enough to shake the enamel off your teeth, so you've got to be able to hold them securely. A groove above the pistol grip lets you wrap your palm firmly around the drill body so you can exert direct, efficient force from your elbow to the tip of the bit. This leaves your ring finger and pinky free to pull the trigger. Thankfully, all the tools we tested have grooves above their pistol grips, and large, easy-to-reach triggers, but some tools feel different. The DeWalt, Freud, and Milwaukee tools have padded pistol grips that noticeably absorb vibration. I think users with smaller hands will find these tools and the Metabo, Bosch, and Hitachi models as comfortable as a hammerdrill can be.
Chuck and Key. I know two guys who have cordless hammerdrills with keyless chucks; they've both switched them out for keyed models. It's just not possible to crank down hard enough without a wrench to keep a chuck's jaws engaged. But that might not be true for long; new keyless chuck designs are just around the corner. All of the chucks in this group are 1/2-inch, heavy-duty keyed devices. Eight of the manufacturers in this test outsource their chucks. Only Metabo makes its own.
Some notes on chucks: Keep them from seizing by regularly cleaning out dust with compressed air. Forget about oiling a chuck if it gets stiff. The lubricant will only attract and hold more dust. It would be nice if the steel rim on the front of the chuck was case-hardened. We burst through slabs during several of our applications, and the chuck hammered down on the material with the strength of a carpenter pushing for all he's worth. The chuck's steel is scored, and I suspect it might break if it regularly beat down on material.
A big chuck key is important for comfort and proper bit clamping. The Bosch, Hitachi, Metabo, and Porter-Cable tools have the best keys; they're about 4 1/2 inches long. It's nice to have a large, comfortable chuck key, and it's equally nice to have a convenient place to store it. Most of the tools we tested store their keys in molded slots at the bases of their pistol grips. Metabo went the extra step and slotted a space for driver bits, too. The Porter-Cable, Milwaukee, and Hitachi models still use strips to hold their keys on the cords.
Switches. We wear gloves when running these tools, so models with the largest switches were the most convenient to use. Eight of the units we tested have large dials or levers to switch drilling speeds and hammer modes. Makita uses a collar behind the chuck to change hammer modes and a side-mounted dial to vary speed; neither is easy to operate while wearing gloves.
All the models provide trigger locks; the best ones don't lock-on accidentally. Recessing the button or positioning it so your other hand operates it eliminates that problem. The Makita, Porter-Cable, Milwaukee, DeWalt, and Metabo tools have well-designed locks.
BPM. Blows per minute–the number of times the chuck is struck from inside the drill–vary widely in this field, but offer no noticeable performance difference. All the tools operate with nearly equal power in wood and concrete. Our shop tests showed that it took them an average of 6 seconds to drill through a concrete block, 77 seconds to drill 8 inches of concrete, 6 seconds to get through a really old 8-inch Doug fir timber, and 3 seconds to get through pressure-treated 4x4s.
All of the hammerdrills we tested are professional, heavy-duty units that could easily provide years of dependable service. All are equally powered, but design and balance features tipped the scales. Our best beast was DeWalt's DW515, which scored high in all areas: good balance, excellent side handle, padded grip, and easy-to-operate control knobs. Metabo's 751 comes in a close second because of its fine balance, good switches, and clever side handle. The rest of the pack literally shakes out like this: Bosch 1194AVSRK, Porter-Cable 7751, Fein 638, Hitachi DV20V2, Freud FPD182R, Milwaukee 5378-20, and Makita HP2010N.
Don Geary is a tool tester and freelance construction writer living in Baker, Nev.