Cool Tools: Rotary Hammers
Published: January 2008
Electricians frequently must make holes in a variety of materials—easy-to-cut Sheetrock, wood, masonry, concrete and different types of metal with varying degrees of hardness—and many are beyond the capabilities of the conventional rotary drill.
There are, however, specialized tools and cutting accessories made to quickly and efficiently drill into even the hardest substances while minimizing the amount of physical effort required. The most difficult cuts call for a hammer drill or rotary hammer.
The tools are not the same, although the differences between the two may not be clear. Comparing the two, a hammer drill chips, and a rotary hammer pounds. A hammer drill “hits” more often, but with less force than a rotary hammer. Hammer drills are more appropriate for making holes in block or brick; the rotary hammer is better for drilling holes in dense poured concrete.
In addition, the internal mechanisms of the two tools are different.
In hammer mode, the hammer drill employs a mechanical cam-action drive that delivers rapid, low-impact blows per minute (BPM), best suited for small-diameter holes in soft masonry, metals and other materials of hardness that are difficult for conventional drills.
Rotary hammers—the topic of this report—work like a hammer and chisel with lower BPM but much higher impact energy for drilling broader diameter holes—¼ inch to 6 inches—depending on the type of rotary hammer. Unlike hammer drills, which use a round shank drill bit, rotary hammers accommodate a variety of special shank drill bits. Unlike hammer drills, a rotary hammer does not require the user to exert manual force during drilling.
There are several sizes and types of rotary hammers, and the application dictates which is best suited for the job.
Bosch Tools, Mitch Burdick, product manager—concrete: “Rotary hammers are specifically designed for drilling into concrete all day long. They have a piston and a striker pin, which interface with the drilling function of the tool, providing the necessary impact force on the bit for penetrating the concrete. This is especially important in locations such as Las Vegas, the Pacific Northwest and the Northeast, which have a hard aggregate in the concrete. Rotary hammers also feature an innovative chuck system designed specifically for drilling into concrete all day long. Most rotary hammers have three modes of operation: Drilling with hammer action is most common; hammer only for occasional chipping and demolition; and drill only, rarely used, but offering versatility for drilling in materials other than concrete.
“Sizes of rotary hammers range from ¾ inch to 2 inches with 85 percent of the drilling needs of electricians within the range of 3/16 to ½ inch. The most commonly used rotary hammer is the 1-inch model, which has an optimum drilling size of ? inch.
“Because rotary hammers are used in all-day applications, the most common changes in rotary hammer designs have been with ergonomics and power-to-weight ratio. Ergonomics involves size and shape of the main handle to maximize comfort of the hand grip area, the shape of the tool for multiple grip locations, the size and length of the tool to improve tool balance while in use, and the size/weight of the tool for a given level of power to maximize productivity while minimizing worker fatigue. In addition, reduction of tool vibration levels is gaining increasing attention as a means to further improve worker comfort.
“Dust-collection systems can be especially helpful if a significant amount of drilling is being done overhead, where gravity puts the dust in the worker’s face, or on job sites where only part of the building is being worked on, and the rest of it is in use.
“Leading manufacturers offer cordless models, and drilling speed and tool durability are two of the most important factors to consider—cordless tools must perform equal to their corded counterpart.”
DeWalt, John Goebel, associate product manager: “Electricians often use a wider variety of rotary hammers than any other trade. Compact SDS hammers are the most common type of rotary hammers for electricians. However, electricians also use SDS max/spline hammers frequently.
“Rotary hammers do not pound in rapid succession as fast as hammer drills, but the BPMs generated by a rotary hammer have much greater force, usually referred to as ‘impact energy.’ Because rotary hammers have far superior impact energy than hammer drills, they do not require nearly the amount of BPM as a hammer drill, and users of rotary hammers do not need to apply the same amount of pressure to the drilling application as required with hammer drills—the operator lets the tool do the work and experiences less fatigue.
“Deciding whether a concrete drilling application requires a hammer drill or rotary hammer is contingent on three factors: depth and diameter of the hole, hardness of the material, and the number of holes drilled. Because rotary hammers utilize an electro-pneumatic system to create a superior amount of impact energy, they have the ability to drill larger holes in harder types of concrete aggregate.
“[The] popularity of cordless models is growing rapidly. The impact of lithium-ion battery technology on rotary hammers is significant, providing greater impact energy and more holes per charge.
“Durability is the No. 1 user requirement for rotary hammers. As with other power tools, rotary hammers have evolved to be more powerful and productive. One trend in tool design is to incorporate a mechanism to control the amount of vibration generated by hammer drills to make tools easier and less tiring to use.”
Hilti USA, Subroto Pyne, senior product manager: “There is confusion between rotary hammers and hammer drills because many suppliers and users use the terms interchangeably. However, describing the mechanism of each tool is a distinction universally used: ‘electro-pneumatic’ [rotary hammers] and ‘cam-action’ [hammer drills]. Cam action provides the hammering function through a metal-on-metal toothed cam, whereas the electro-pneumatic principal uses a piston and air pocket.
“Rotary hammer electro-pneumatic tools require less effort to use and typically provide extended life due to less wear and generally are preferred over cam-action drills where repetitive drilling in concrete or masonry is required. Smaller electro-pneumatic rotary hammers use drill bits with SDS plus connection ends, extending life and rebar resistance when drilling in reinforced concrete.
“Drilling performance and ergonomics of rotary hammers have improved. Big changes have come in the areas customers asked for: Higher capacity batteries allow more cordless applications, dustless drilling and chipping performance similar to corded tools. Customers now have a choice of cordless rotary hammers, including models powered by lithium-ion batteries.”
Makita USA, Anthony Corwin, industrial and commercial product manager: “Although all trade groups use light rotary hammers to drill small anchor holes, the two key user groups are electricians and mechanical contractors. Electricians repeatedly drill holes for anchors and equipment. They also drill or core through hole penetrations and drive ground rods with large rotary hammers. Chiseling is common among electricians either to open large holes or to clean up. With such variety and high-volume requirements, electricians need durable versatile rotary hammers.
“Rotary hammers have not had major design changes. However, they are becoming lighter, and some models include added features, such as LED lights for better visibility. Antivibration technology not only reduces tool vibration but lowers noise levels and makes more efficient use of power.”
Milwaukee electric tool corp., Eric Fernandes, group manager: “Utilizing a piston, rotary hammers generate significant impact through the bit to the end of the bit to pulverize the concrete into dust, which is then carried out of the hole by the flutes. Impact delivered from a rotary hammer is much greater than that of a hammer drill, allowing it to drill faster and larger holes in concrete. When there are a large amount of anchors that need to be used in concrete, rotary hammers make more sense because they can do the job faster and with less effort.
“Electrical applications for rotary hammers include drilling holes for concrete anchors into ceilings and walls to hang cabling systems, lighting systems, and for junctions boxes; core drilling through concrete floors for telecom and datacom wiring; drilling through walls for conduit; chiseling corrective holes or enlarging holes through block walls; and driving ground rods into the ground.
“Rotary hammers are basically identified by tool reception:
- SDS-plus hammers are typically used to drill holes for anchors and a maximum hole sizes of up to 1? inches in concrete.
- SDS-max and spline hammers are used for larger holes, up to 2 inches and deeper that require greater impact energies.
- SDS-max and spline hammers are also used for other operations like core drilling and chiseling and demolition work.
“Many commercial electricians working on commercial jobs frequently use SDS-plus hammers for drill and fill applications. A compact 1-inch SDS rotary hammer makes very quick work of typical anchor sizes, ranging from ¼ to ? inch.
“There has been a big focus on end-user comfort and reducing the amount of vibration felt by the user when using rotary hammers. We will continue to focus on making users more comfortable, which will also lead to greater productivity on the job.”
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or email@example.com.