Drilling holes is a routine task for electricians, and few electrical contractors (ECs) go to a job site without a good cordless drill in his or her tool kit. The basic drill is fine for drilling in wood and other soft materials, but, when working on harder surfaces—masonry, brick, cinder blocks and soft metals—a hammer drill does the job faster and more efficiently. In the “drill” mode, the hammer drill operates as a standard drill. Switching to the “hammer” mode, the tool delivers rapid hammering blows to drive the bit through harder surfaces.


Not so long ago, cordless tools provided convenience but lacked the power of corded models of comparable sizes, and a battery charge couldn’t last long enough for dependable productivity.


That has changed with lithium-ion batteries, new brushless motors and other improvements. Most manufacturers say cordless hammer drills now match or exceed the performance of corded products. Even small 12-volt (V) lithium-ion “pocket” models pack a lot of drilling power and can be carried on a tool belt or in a pocket.


Hammer drills also have their limits. They work best on “softer” hard materials. For really difficult drilling, a rotary hammer is more productive. Experienced tool users have learned when to switch from standard drill to hammer drill and when a rotary hammer is the best tool for the job; these practices result in more efficient work, and the tools last longer.


Operating components of hammer drills and rotary hammers are completely different. Hammer drills are dual-mode tools with a mechanical cam-action drive. During drilling, the operator must apply pressure on the tool. Electro-pneumatic rotary hammers generate impact force internally and are designed for drilling in hard concrete.


Hammer drills deliver a high number of blows per minute with relatively low impact energy. Rotary hammers produce fewer blows per minute but with much higher impact energy, and they can produce a broader range of hole sizes—from diameters of ¼ inch to 6 inches—depending on the size of the tool and bit. Hammer drills use a round shank drill bit, while rotary hammers use special shank bits, including SDS+, spline and SDS Max.


Those in the electrical industry are familiar with some hammer drill manufacturers: Bosch (www.boschtools.com), DeWalt (www.dewalt.com), Greenlee (www.greenlee.com), Hilti (www.hilti.com), Hitachi (www.hitachipowertools.com), Makita (www.makitatools.com), Milwaukee Tool (www.milwaukeetool.com), Porter Cable (www.portercable.com), Ryobi (www.ryobitools.com) and others.


Representatives of four of those companies comment on today’s hammer drill products.


Aaron Brading, business unit manager, power tools and accessories at Hilti, said: “Lithium-ion technology has greatly advanced the capabilities of all cordless tools, including hammer drills. It has allowed manufacturers to increase the amount of energy packed in their batteries without increasing the size (larger gas tank in your car without your car getting heavier) and has made the cordless industry less sensitive to performance in cold weather climates.


“Cordless tool performance can typically be qualified into two categories: application speed and how much work per charge. In some of our classes, cordless tools have exceeded the drilling speed of corded tools in the same category, which addresses application speed. While corded tools have no effective measurement for work per charge, it can be said that, in a lot of cases, a cordless hammer drill can meet a day’s worth of work in one 
single charge.


“Internally, what may not be as obvious to the user has been the shift to brushless motors, which not only allow better performance but also better lifetime of the tool. Traditionally, power tool motors have had epoxy-coated copper windings and carbon brushes. When drilling through concrete, very abrasive silica dust is created and can get back inside the tool. Since the motor is spinning at an extremely high rpm, this dust can tear through the epoxy coatings and abrade the brushes, causing the motor to fail. Brushless motors are much less sensitive to this vulnerability.


“With regards to functionally, we’ve seen the inclusion of on-board LED lights and a development of chipping functionality. Last year, Hilti introduced the industry’s first cordless combihammer, which makes it feasible to handle more than just corrective chiseling and would actually allow an electrician to drill a 1-inch through-hole in a concrete wall and widen the hole with a chisel to allow the passage of larger outside diameter EMT,” Brading said.


What sets Hilti hammer drills apart from other products?


“Hilti will repair or replace [a] tool, battery, or charger at no cost to the end-user, shipping included, due to manufacturer’s defects for two years with normal wear and tear. This brand promise does not allow Hilti to compromise on the quality of the tools it sells,” Brading said.


Mario Lopez, cordless products manager, Makita USA, said: “18-volt lithium-ion battery technology gives electricians several advantages over older battery technology, including superior power-to-weight ratio. With efficient brushless motor technology and 18V lithium-ion batteries, cordless tools are pushing new limits in performance and run time, allowing more contractors to ‘cut the cord.’ Charge time of new lithium-ion batteries is shorter, run time longer, so the battery spends more time working and less time sitting on the charger.


“Advances in brushless motor technology are yielding new benefits for contractors, especially electricians. For common applications that require three-inch hole saws and ⅞-inch Forstner bits, brushless hammer driver/drills are breaking new ground. Our new XPH07M hammer drill provides 1,090 inch-pounds of torque. The key is the controller, which acts as the ‘brain’ of the tool and monitors the flow of energy for increased power, speed and efficiency.


“Today’s hammer drills offer superior ergonomics. For example, old stem-style batteries extended into the handle of the tool, and engineers were forced to design the tool’s handle around the battery. With 18V slide-style lithium-ion batteries, engineers are able to design the tool’s handle around the human hand, which means superior fit and comfort,” Lopez said.


What sets Makita hammer drills apart from other products?


“Performance and run time, charge time, superior ergonomics, and breadth of line,” Lopez said.


Cole Conrad, product manager, 
Milwaukee Tool, said: “When the need is to drill in concrete, there are two power tool options: the hammer drill and rotary hammer.


“Hammer drills are a great all-around tool for electricians because they can be used in either drill-drive or hammer mode to do multiple daily applications. In the hammer mode, a hammer drill delivers a percussion motion that is created by hammer plates spinning against one another.


“A hammer drill is ideal for drilling smaller holes into soft aggregates like cinderblock. Electricians use the tool in the hammer mode to drill small-diameter holes (¼-inch and smaller) in concrete for anchors. For larger anchor holes and through-holes in concrete, users should switch to a rotary hammer. While a hammer drill rotates faster than a rotary hammer, it does not hit as hard.


“With all of the power that is available in today’s lithium-ion battery packs, tool manufacturers will continue to be able to challenge conventional wisdom about what types of tools can be effective cordless solutions. Milwaukee’s high-performance M18 fuel model certainly can compete with corded counterparts in the hammer drill category.


“Coupled with the continued advancements in gear and motor technology, tools are getting smaller, more powerful and overall delivering greater productivity to the user without sacrificing durability.” 


“With the combination of its brushless motor, lithium-ion battery pack, and Redlink Plus intelligence, our M18 Fuel hammer drill will outperform other 18V drills and perform as well or better than corded counterparts and is lighter and 1 inch [shorter] than its leading competitor,” Conrad said.


Sarah Peeples, product manager, Porter Cable: “Hammer drills are most frequently used by electricians to install electrical boxes and other fixtures into brick and block walls. Because the hammer function can be turned off and on, it can operate as a standard drill driver for other nonmasonry applications. For larger holes and for working in concrete, a rotary hammer would be more suitable.


“Lithium-ion batteries provide compact power. [Nickel-cadmium (NiCd)] batteries were large and bulky, and lithium-ion packs more power into a smaller package. The life of the batteries is sustained longer, creating a more efficient battery compared to NiCd. One result is that hammer drills have moved into the compact drilling category, creating a smaller, lighter weight hammer drill option for tool users.


“Cordless hammer drills powered by lithium-ion batteries provide convenience and power. However, when larger holes are required and numerous holes must be drilled, a corded hammer drill will provide more sustained power. A cordless hammer drill provides convenience and power,” Peeples said.


What sets Porter Cable hammer drills apart from the competition?


“The Porter Cable 20V Max hammer drill delivers power that stacks up to the competition in a compact size. The tool is powerful and lightweight; it can be used daily with little fatigue, and its 2.0 Ah batteries provide extended run time,” Peeples said.


With the proliferation of lithium-ion battery technology, hammer drills have come into their own as convenient tools, which manufacturers, such as these, will continue to innovate.