The long and short of demo hammers

There is not much middle ground in the demolition world, particularly where power tool manufacturers are concerned. In their eyes, if you’re not running a 70-lb. jack hammer, odds are you are using a 15-lb. combination rotary/chipping hammer. Which tool you choose depends on what you do most often.

“Most general contractors don’t do just demolition all day, so instead of using a heavy tool like a 35- or 70-lb. breaker, they use combination tools, large rotary hammers, that can do demolition in addition to drilling,” says Anthony Corwin, product manager for commercial and industrial products for Makita. “Combination tools give them more bang for the buck.”

Corwin points to Makita research to back this up. According to its user studies, Makita’s popular model HR4010C, a combination hammer that weighs in at just 13.9 lbs., is used as a rotary hammer roughly 70 percent and as a demolition tool about 30 percent of the time.

As a result, most manufacturers focus research on tools that weigh less than 20 lbs. or more than 35 lbs., although manufacturers offer a broad choice of tools for the job across the entire weight range.

Power vs. durability
Traditionally, tool durability has been the No. 1 concern of rotary and demo hammer users.

“When you’re talking about hammers, you’re talking about removal rate and durability,” says Mitch Burdick, Bosch product manager for concrete hammers. “Removal rate is best measured as the impact force generated by the hammer.”

Unfortunately, the very nature of rotary and demolition hammers puts these two criteria at odds with each other. Sooner or later, a tool that pounds concrete into dust will beat itself into pieces, too.

“It’s a balancing act,” Burdick says. “A great deal of engineering goes into creating a design that optimizes impact force and durability. You can build a tool that hits harder than anything out there, but it will beat itself up and break. That’s not what the user wants.”

The opposite is just as bad; a tool designed for durability at the expense of impact force will have a slow removal rate and lower productivity. To marry such warring physics, engineers endlessly combine design and component elements to improve both striking power and durability without favoring one at the expense of the other.

Vibration vs. the user
Demolition and rotary hammers are well-known for beating up their operators, too. As industry awareness of the hazards of vibration exposure grows, so do the national and international restrictions on use of such tools — and the pressures on manufacturers to make offending tools safer to use.

Engineers face a tradeoff between maximizing the impact force a tool generates and minimizing the health impact of the vibration it creates in the process. And, while trade names such as Anti Vibration System and Anti Vibration Technology used by different manufacturers sound alike, the solutions they present are different.

Makita’s Anti Vibration Technology (AVT) is a counterbalance design based on damping science, developed in seismic research to absorb shocks and protect buildings. Makita’s AVT dynamic damping involves reciprocating engineering where a mechanical damper, effectively a counter balance weight, provides an equal and opposite anti-vibration force. As vibration is eliminated, power efficiently increases. Without the dissipation of power through vibration, more of the generated energy in the motor can be delivered to the tool bit.

“We strive to make our tools more comfortable and more efficient for the end-user,” says Corwin. “Reducing vibration is a great example of this, so we offer AVT in our HM1810 70-lb. breaker hammer and in our HR4010C combination hammer.”

Euro-influence
Milwaukee Electric Tool’s AVS (Anti Vibration System) hammers, designed in Germany to meet ergonomic standards that are stricter than those in the U.S., utilize a system of active dampers and springs in main and side handles to reduce the amount of vibration that reaches users’ hands and arms. Milwaukee says AVS reduces vibration by up to 50 percent.

“Europe’s Hand And Arm (HAV) vibration regulations dictate how many hours a day a user can use a vibration-generating tool,” says Eric Fernandes, product manager for Milwaukee Electric Tool. “If the vibration is high, the number of hours that tool can be used during the day are lower.”

Milwaukee posts information on hand and arm vibration symptoms, injuries, legislation and more at www.milwaukeetoolvibration.com. The site also contains a vibration exposure calculator.

“The American National Standards Institute (ANSI) has recently adopted similar standards, and while there are not yet any specific regulations in the U.S., the European standards are clearly driving tool development,” adds Joe Fedor, product manager of industrial tools at Hitachi.

Two tools Hitachi is launching this month feature its User Vibration Protection (UVP) system. The H45MRY demo hammer is a lightweight SDS Max hammer. Its corresponding 1 9/16" combination hammer is the DH40MRY.

“UVP features a floating counterweight behind the motor that reacts to the movement of the tool, not just the piston,” Fedor says. “Our new tools also have separate systems in the top and the bottom of the main handle so the handle is not rigidly attached to the body of the tool but rather is its own floating system. This further reduces vibration.”

BOSCH makes the “Jack” breaker hammer that hits with an unprecedented 34 ft.-lbs. of impact force, but weighs just over 35 lbs. Its Active Vibration Reduction System (AVR) dissipates vibration by 40 percent over its closest competitor. Item 131

The Bosch system, called Active Vibration Reduction (AVR), is a two-handle design.

“There are two basic places where vibration occurs: in the hammer mechanism where the force is created and in the handle and wherever the grips are on the tool,” Burdick says. “We reduced handle vibration in our small and medium-sized hammers several years ago, but you can only take so much vibration out at the handle.

“With ‘Jack,’ our new 35-lb. demolition hammer, we went back to the hammer mechanism and reduced the vibration at the source.”

To do this, Bosch engineers optimized the buffer between the striker and the piston, thus reducing vibration at its source, while maximizing impact force. In addition, the vibration-reducing main handle uses rubber material that isolates the handle from the tool body and a spring-based shock-absorbing handle.

Bosch says this adds up to a vibration reduction of at least 40 percent vs. its nearest competitor.

“There’s no one overriding technology that achieves it,” he says. “Many engineering and evaluation aspects must balance each other.”

DeWalt breakers and rotary hammers are also designed in Germany, so it too is keenly aware of the influence of European guidelines on tool research; and the proof is in the hammer. DeWalt’s D25980K 70-lb. breaker, new this year, exemplifies this multi-pronged approach to vibration reduction. Its SHOCKS Active Vibration Control system uses automotive-grade seals, rubber mounts, shock-absorbing handles, spring systems and counterbalanced hammer mechanisms to reduce vibration by up to 65 percent.

“Amazingly, some users don’t even complain about the vibration from demo hammers because they don’t realize there could be another solution,” says Eric Bernstein, director of product marketing, concrete, for DeWalt. “But when we let them run a D25980K for even two minutes, the only word to describe their response is ‘giddy.’ We truly believe this tool will change the standard of living for users who break up concrete for a living.”

Such vibration-reducing technologies not only save significant wear and tear on the user, they save the tool, too. Anti-vibration technologies mean today’s rotary and demolition hammers can last up to twice as long as their predecessors.

Serviceability
Even the most durable tools break down. Given their high cost, typically $750 or more, hammer tools are expected to be not just workhorses but easily-doctored workhorses in the bargain.

“Users want these tools to be easy to service,” Fernandes says. “We make our tools modular. Loosen six screws and you can take off the top gear case cover and access all major components. If you need to replace an O-ring, for example, it’s very easy to do and get it back on the job.”

Published in the September/October 2007 issue of Contractor Tools and Supplies magazine.