Published: September 2004
Hammer/drills are essential tools routinely used by electricians who do wiring and cabling. In many instances, there is no better power tool for drilling holes for anchors to mount boxes, panels or conduit, or drilling holes in for conduit runs.
Hammer/drills are two tools in one: with the flip of a mode-selector control, a hammer/drill converts from conventional drill for working in wood and soft materials to a hammer/drill for drilling in masonry, cinder blocks, concrete, metal or virtually any other material.
“The key benefit of a hammer/drill is its ability to drill in a variety of materials,” emphasized Tom Vasis, concrete drilling/breaking product manager, Bosch Power Tools and Accessories. “This is the perfect tool for electricians as they encounter many different situations where there is a need to drill through wood or metal studs.
“Sometimes they need to use step drills when drilling into a panel box and the drill-only mode is perfect. Or it may be necessary to drill through flooring or ceilings during installations. And the hammer mode is perfect for mounting anchors in brick or concrete when installing electrical boxes. A simple drill may be able to handle many of these situations, but when it comes to concrete or masonry, a hammer/drill provides a clear advantage.”
Most major power tool companies offer hammer/drill models and whatever the brand, buyers will find today’s models provide more power in smaller, lighter-weight tools. As with other power tools, cordless models are growing in popularity.
The term “hammer/drill” often is mistakenly used interchangeably with rotary drill and sometimes even confused with demolition hammers.
The inner works of hammer/drills and rotary drills are completely different. For this report, we define hammer/drills as dual-mode tools with mechanical cam-action drive tools that can drill in a variety of materials and require the user to apply pressure to drill. Electro-pneumatic rotary hammers generate impact force internally and are designed for drilling in concrete.
“Hammer/drills and rotary hammers are designed differently to meet different needs,” explained Eric Bernstein, DeWalt product manager for rotary and demolition hammers.
“Hammer/drills deliver high blows per minute (BPMs) and low-impact energy, and are best suited for small-hole diameters from 3/16 inch to 1/4 inch optimal,” Bernstein continued. “They are ideal for holes in softer material such as concrete block.
“Rotary hammers use lower BPMs but much higher impact energy that provides performance in a much broader diameter of holes—1/4 inch to 6 inches—depending on the type of rotary hammer. Unlike hammer/drills that utilize a round-shank drill bit, rotary hammers use special shank drill bits such as SDS+, spline and SDS Max.”
Generally, hammer/drills are used for lighter drilling of small-diameter holes and rotary hammers on jobs where multiple holes of larger diameter are drilled in concrete.
Hammer/drills are not demolition tools.
“Hammer/drills are not for demolition work, because they only drill rather than chip or break,” said Bosch’s Vasis. “Electricians should consider one of two options for light to heavy demolition work: a combination tool or demolition hammer.
“Similar to the hammer/drill, combination hammers offer multiple modes: rotation only, rotary hammer and light chipping. Combination hammers come in various sizes, but most are only for light chipping applications. They often fit the various needs of electricians, but as material-removal needs increase, electricians should consider looking toward full-fledged demolition hammers, or even breakers, tools that only use reciprocating motion to chip and break.”
Selecting the best hammer/drill model or using a rotary hammer instead, depends on the application for which tools will be most often used.
“Pick a model whose capacity rating best matches the common hole size that will be drilled,” said John Sara III, cordless tools product manager, Milwaukee Electric Tool Corp. “If you spend most of your time drilling small-diameter holes into concrete, consider a 3/8-inch model. Its high rpms and higher BPMs drill small diameter holes in concrete greater than any tool on the market.”
“Larger diameter holes,” Sara continued, “require electro-pneumatic rotary hammer models. These units can drill an occasional small diameter hole, but the speed tends to be too slow for production work. The larger tools are for larger diameter holes that require tools with more powerful motors.”
As with most any application, matching tool to specific job requirements maximizes efficiency.
Bosch’s Vasis said: “Usually smaller hammer/drills are a better option for shorter drilling projects where only a few holes are necessary; this is often the case for electricians.”
The time to switch up to a rotary hammer comes when projects call for 10 holes or more in concrete. The internal mechanism inside a rotary hammer actually produces impact force as pressure moves back and forth slamming against the end of the carbide drill bit. As a result, these tools can be much more efficient in mass drilling situations. As hole diameters and depths become larger, specific optimal drilling ranges and rotary hammer sizes also grow. “Overall, knowing the difference of which tool to use can make a world of difference when it comes to efficiency and speed.”
The continuing evolution of hammer/drill technology makes them more productive and easier to use.
“Hammer/drills have become much smaller with a lot more power,” said Keith Kirk, mechanical/electrical market manager, Hilti Inc. “In combination with some of the newer drill bits on the market, drilling rates have also increased. In addition, some tools are available with additional operator protection such as torque control, a feature that stops the tool if it begins to turn too quickly, such as may occur if the bit gets lodged into rebar or hard aggregate.”
Eric Weston, Porter-Cable associate product line manager, believes tool weight is a key issue. “Every day,” he said, “power tool companies are trying to find ways to take weight out of not only hammer/drills, but their entire range of products. Whether it is using cast aluminum, composite materials or magnesium, tools continue to get lighter. If a buyer has to carry a tool around all day, weight plays a big part at the time of purchase.”
Sara said Milwaukee expects the shift from corded to cordless hammer/drills is a trend that will continue.
Weston had this to say about cordless models: “Cordless hammer/drills are becoming more popular, as are most cordless tools. Cordless hammer drills are great when you have a small number of holes to drill because it stops you from having to find a power source and run an extension cord to complete what should be a quick job. However, there are drawbacks to cordless hammer/drills, too. If you are drilling into some type of reinforced materials cordless model may not have the power needed and if you are doing a lot of drilling, the battery will drain much quicker.”
Bernstein describes the cordless rotary hammer market as exploding.
“More and more users are seeing the labor and material benefit from going corded to cordless,” he continued. “The time a user takes setting up, tearing down and replacing cords along with the cost associated in replacing worn extension cords usually makes the cordless rotary hammer pay for itself in less than six months.”
Hammer/drills and rotary hammers continue to evolve.
“Power climbs in amps, and speeds and torque have increased for greater productivity,” said Vasis. “Weight has been reduced somewhat, but more importantly, balance has improved. Also, some manufacturers offer fully synchronized gear boxes which improve tool life and make for much easier shifting. Another important point is a slip clutch. When a bit becomes jammed there can be a reverse torque reaction and an anti-rotation clutch greatly reduces this torque reaction.” EC
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or firstname.lastname@example.org.