Cool Tools: Rotary Hammers
Published: November 2011
When electricians and other tradesmen need to drill holes in surfaces too hard for conventional drill/drivers, they have two options: a hammer drill or rotary hammer.
A hammer drill has a mechanical cam-action drive that delivers rapid, low-impact blows well-suited for drilling small-diameter holes in soft masonry, metals and other materials. A rotary hammer generates higher impact, less frequent blows per minute (BPM) to make larger holes—up to 6 inches in diameter—in concrete, block and brick.
Rotary hammers accommodate a variety of bits and hit like a hammer and chisel—the tool does all the work, sparing the user from applying any manual force. There are three basic types of rotary hammers. The application will dictate which type is the best for a job.
Special Direct System plus or SDS+ hammers typically are used to drill holes in concrete for anchors with maximum hole sizes of 11/8 inches; SDS-max and spline hammers are for larger diameter, deeper holes and are used for other operations, such as core drilling and chiseling and demolition work.
Electricians use rotary hammers for making holes in concrete or block and brick to install anchors for conduit clips, junction boxes and cable trays and to make through holes for conduit.
As it has applied to other power hand tools, lithium-ion technology is included with rotary hammer designs. Today’s models are smaller and lighter in weight, but still deliver the power to do tough jobs. Manufacturers say another major difference in current models is improved dust-collection systems.
Bosch (www.boschtools.com), Mitch Burdick, product manager, hammers and vacuums, said: “The main considerations for choosing between a rotary hammer or a hammer drill are size of the job, the type of materials being worked on, and the frequency of the application—will it be all-day, every day or infrequently? A rotary hammer is a dedicated tool for drilling or chiseling in concrete and is designed for all-day use for medium to heavy duty jobs—its hammer mechanism creates the necessary impact energy for these applications.
“Compact size and lighter weight are common trends seen across all cordless- tool platforms, but the big challenge for manufacturers is to achieve more compact and lighter weight tools without sacrificing power and performance.
“Rotary hammers are being continuously improved regarding increased impact energy and performance while adding little to no weight. Low vibration technologies are being added to most hammers in a given product line to improve the comfort of using the tools in all-day applications. The focus here is to increase productivity and reduce the wear and tear on the contractor who has to use these tools all day long.
“Thanks to lithium-ion battery technology and advances in motor technology, today’s generation of cordless rotary hammers are capable of delivering near-corded tool performance, and a major benefit to using lithium-ion technology is that you’re able to deliver considerably more power in a lighter, more compact size. This means big benefits for tools like rotary hammers, which are typically bigger and heavier by nature. And when you’re using these types of tools in tight, confined areas, a lighter weight and more compact tool is preferred.
“The Bosch RHH180 18V rotary hammer incorporates brushless motor technology as well as electronic motor protection [EMP], which protects the tool from overload and overheating, which can damage the tool and battery. Brushless or EC [electronically commutated] motors are much more compact and lighter weight than traditional motors used in power tools, and they’re designed to deliver the same power and performance. A brushless motor has a sealed design, which prevents contaminants like dust and debris from damaging the motor,” Burdick concluded.
DeWalt (www.dewalt.com), Jeff Beck, rotary hammers product manager, said: “The biggest improvements in rotary hammers today are dust management and tool control. In the area of dust management, we are seeing more contractors wanting to limit the amount of dust created by rotary hammers. Attention is growing as contractors become more concerned about inhaling airborne concrete dust. Last year, DeWalt launched a cordless dust extractor (that fits the 36V SDS hammer), and a dust extractor telescope with a hose, which fits most of our SDS hammers and attaches to a vac or dust collector. Later this year, we will introduce dust extractors for larger hammers as well.
“By ‘control’ is meant improved tool control by reducing vibration and ‘bind up’ when a bit gets jammed. We have 17 models with an active vibration-control system that reduces vibration by up to 50 percent compared to standard units, and the lower the vibration on the tool, the lower the fatigue on the user.
“In addition, DeWalt also has four combination rotary hammers and chipping hammers that feature a patented two-stage clutch, which allows the user to set the torque level in drilling mode to a higher or lower setting based on the application.
“The cordless market for rotary hammers continues to grow as battery technology changes and improves. Because lithium-ion batteries are lighter than comparable NiCad batteries, there is an ergonomic advantage for the user.
“Each type of rotary hammer has a specific bit determined by the shank. All SDS+ hammers take a bit, which has a shank of about 3/8-inch in diameter and has two long grooves and two indents cut into it. A SDS max bit looks like a supersized SDS+ bit because the shank is about 5/8-inch in diameter, but it has three grooves instead of two. A spline bit looks very different as it has 12 splines on the end of the shank,” Beck said.
Makita (www.makitatools.com), Adam Livingston, commercial products manager, said: “With rotary hammers, we see three clear trends on job sites: the demand for less vibration, better dust extraction and more compact tools for applications like overhead work.
“Vibration reduction is moving beyond spring-loaded detached handles, and there are much better results with systems that actually reduce vibration from within. Makita is leading this innovation by being one of the only manufacturers to engineer vibration reduction inside the tool. Makita’s antivibration technology is an internal counterbalance system that is engineered inside the tool for more significant vibration reduction.
“Contractors are demanding more dust-extraction solutions to reduce the amount of concrete dust created during tool usage. New attachments, including Makita models recently released for our SDS+ corded and cordless hammers, are engineered to help reduce the dust created from drilling without compromising tool performance. There are several advantages to attachments over built-on systems. Built-on vacuum motors share power with the tool, which can reduce impact energy [and] decrease the tool runtime. Attachments can be used with most job site vacuums, eliminating components being attached to the tool, which is more compact and has less weight than most built-on systems. Lastly, most built-on systems have only a half-gallon capacity, increasing downtime from more frequent disposal of the collected material.
“Cordless rotary hammers are being used more frequently on job sites. The power-to-weight ratio of 18V lithium-ion has proven to be extremely beneficial in the rotary hammer category, making them ideal for applications like overhead work, where a more compact tool with less weight is preferred,” Livingston said.
Milwaukee Electric Tool Corp. (www.milwaukeetool.com), Rick Gambaccini, group product manager, said: “Rotary hammers have a slower rpm than hammer drills, but they hit much harder. The greater impact energy allows them to drill larger holes, into harder aggregate and is much easier on the user. Bits for the three main rotary hammer retention systems—SDS+, SDS-max, and spline—are widely available in the marketplace.
“With all of the power that is available in today’s lithium-ion battery packs, manufacturers will continue to be able to challenge conventional wisdom about what types of tools can be effective cordless solutions. With this increase in power, and more importantly, the runtime that advancements in lithium-ion now offers, rotary hammers are a viable cordless option.
“With continued advancements in gear and motor technology, tools are getting smaller, more powerful and overall delivering greater productivity to the user without sacrificing durability.
“And utilizing an innovative new gear design, Milwaukee recently launched the new Model 5263-21 compact 5/8-inch rotary hammer that is 10.9 inches long and weighs only 4.6 pounds. It is ideal for drilling overhead and in tight spaces and powerful enough to drill the majority of holes commonly drilled by the professional trades. By using new technology and designing the tool for a specific trade group rather than the masses, the result is a tool with an ideal power-to-weight ratio for electricians,” Gambaccini said.
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at email@example.com.