By Michael Springer
By coincidence, it was just 10 years ago to this very issue of Tools of the Trade (Winter 1995) that I used a Tool Test to select and buy my 1/2-inch hammerdrill. It has dependably drilled anchor holes in tile, mortar, block, and usually into concrete while faithfully doubling as a two-speed drill for other chores. But if your hammerdrill struggles in concrete packed with heavy aggregate or while using large bits like mine does, and you carry star drills or sharpened masonry nails to break up hard aggregate, then this Tool Test is for you. I tested seven hammerdrill-sized pistol-grip rotary hammers that take concrete and masonry drilling to an entirely new level. My decade-old hammerdrill? I retired it from drilling concrete.
Over the course of 12 weeks, I ran the seven pistol-grip rotary hammers in this group through a gauntlet of concrete and masonry drilling tests both on the jobsite and in a controlled environment–a Department of Transportation facility where they let me drill and chip in old highway barriers with a known consistency in the concrete. I tested the Bosch 11250VSR, DeWalt D25103K, Hilti TE 2-M, Hitachi DH 24PC2, Makita HR2450F, Metabo UHE 28 Multi, and Milwaukee 5383-21. All hammers use SDS (Slotted Drive System) Plus bits (Hilti calls them TE-C bits).
First, I conducted timed tests using new bits in each tool evaluating speed, power, and vibration. Next, I addressed balance, grip, and triggering before taking a close look at the bit holders, depth stops, and clutches. For each tool, I evaluated the owner's manual, toolbox, depth-stop, and multi-use features. The DeWalt, Hitachi, Makita, and Metabo have a chipping function, which I tested for power and performance with different bits. In the end though, drilling holes quickly–with power to spare–influenced my recommendations the most.
Power, Speed, & Vibration
When I buy a tool, I expect manufacturer specifications to be a solid indicator of tool performance. However, some specifications I charted became meaningless when bits were put to concrete. Amp draw, rpm, blows per minute, and even impact energy and drilling capacity ratings didn't correlate with my test results enough to make them accurate predictors of good performance.
Power and Speed. I used brand new 1/2-inch bits drilling very uniform 3,000-psi concrete–an old DOT highway barrier–containing aggregate up to 1-1/2 inches. This test material ensured reliable content made to strict government specifications.
Manufacturers say the best way to get effective results with a rotary hammer is to not push the tool too hard and let the weight of the tool do the work. That is generally true, but because the first thing I see some guys do is push a tool to the limit, I tested the hammers with recommended pressures, as well as hard and extreme pressures in three separate tests looking for drilling power. First, I applied what I call a medium or recommended force to each tool. I drilled four horizontal holes, 4 inches deep, timing and averaging the results. I then drilled four more holes with each tool using what I consider a higher than recommended force. When none of the tools bogged out with higher pressure, I really pushed them to their limits by drilling one hole each with as much force as I could. It's important to note that I am not a test lab with specialized equipment, but the times in the chart (page 60) are as accurate as could be recorded in the field and reflect jobsite conditions.
While pushing a tool hard all day is neither recommended by manufacturers nor realistic for users, my results indicate that the harder I pushed, the faster most of them went. However, this is not a measure of durability. I couldn't test if a tool would last very long being pushed that hard day in and day out. DeWalt says its tool, which finished in the middle of the pack in the speed test, is specifically designed for high-pressure work, not speed. The company says its research indicates that because users overuse the tool, this design increases durability.