Specialty Bits Boost Efficiency for HVAC Installations
Originally published: 08.28.12 by Michael Gerskovich
Proper hammer and bit combination is key to quick, accurate job completion
Concrete, long known for its strength and permanence, is nothing new to the construction industry. But today structural engineers continue to look for new ways to improve the structure and strength of buildings using concrete, and bolstering that concrete with advanced material mixes and reinforcement. As a result of these new material strategies, HVAC contractors looking to maximize their profitability and productivity need to understand the basics of concrete, the systems required to maximize the material, and the correct power tools and drill bits required to ensure accuracy, speed and efficiency.
Getting Down to Business
Many installs and modifications of equipment may involve attachment to concrete or drilling hole penetrations through concrete. While the strength of concrete can vary due to regional differences in aggregate or PSI specifications, it’s becoming commonplace to find high strength concrete that requires precision tools and bits for success. Concrete fasteners, typically used for light-duty loads, are becoming less common, giving way to engineered concrete anchors due to the higher load requirements they can meet and recent building-code changes.
In HVAC installations requiring the use of concrete fasteners or anchors, the type of application dictates the choice of rotary hammer and drill bit. Rotary hammers are sized differently for different applications and they offer a choice of bit-locking systems depending on hole size and torque requirements of the material being drilled. The most common bit systems in use are SDS Plus (referred to as SDS by many), SDS Max and the older Spline system.
Depending on the application, each hammer has a maximum hole size. If you’re drilling a large hole, the user needs a hammer with greater torque and large capacity. Hammer options include inline, where the motor is directly in line with the bit, or drop-down, where the motor is turned at an angle to the bit. Inline is better for applications where the surface is further away from the user and drop-down is better for close-in applications. If the job requires drilling overhead, no one wants to oversize the tool due to the extra weight. The goal is to match as closely as possible the size of the bit to the maximum bit capacity of the hammer.
Typical HVAC applications include hanging pipe, ventilation ducts, suspended fans and generators, and installing finishing accessories. Much of this equipment is suspended overhead using “drop- in” anchors and threaded rod. This common configuration has led to a style of dedicated anchor drilling bit; the Bosch stop bit is an example.
The dedicated anchor bit takes the place of the manual depth gauge on rotary hammers. The bit design integrates a “collar” to prevent over-drilling or drilling into rebar. This provides a more efficient and faster way for the professional installer to employ drop-in anchors properly and securely. The dedicated anchor bit brings precision, speed and professionalism to a task once hampered by guess work and drill bits marked with tape.
The amount of weight to be suspended is the determining factor in properly sizing drop-in anchors and fasteners. Building codes and engineer-approved blueprints take the guesswork out of this on commercial projects, but on small residential jobs the contractor often determines the correct usage of anchors and fasteners based on experience.
Additional guidance is available from the American Concrete Institute, which publishes guidelines for use of anchors and the proper intervals at which they must be set.
Don’t Forget the Core Bits
Core bits are the power tool accessory used to drill holes over the typical maximum size offered by a rotary hammer. They only cut the outside of the hole, and require removal of the “slug” from the middle – especially when they’ve “bottomed out” (when concrete is hitting the bottom of the core bit). Like other concrete bits, core bits incorporate SDS-plus, SDS-max and spline options for or both standard- and heavy-duty applications for rotary hammers.
Many rotary hammer core bits include a new two-piece assembly. This two-piece design and integrated core shank speed up assembly and disassembly, and don’t require the extra step of removing and replacing the pilot bit. Carbide teeth offer faster cutting and longer bit life.
SDS-plus applications include siding, residential vents, conduit and rigid piping. Larger SDS-max core bit applications include running pipes and plastic tubing through cement and concrete, including foundations.
Drilling considerations in HVAC applications
HVAC installations require more overhead drilling than most other rotary hammer applications. Since drilling dust comes down through gravity, installers can attach a dust-boot to the hammer to collect dust effectively.
The use of threaded rods and adhesive (epoxy) for suspending HVAC ducting is common practice. Drilling holes for threaded rods typically requires longer drill bits of six to eight inches to prepare these installations.
Drilling holes for concrete screws is best accomplished using bits with a full-carbide tip for accuracy and durability. Common-sized bits for these applications are 5/32, 1/4 (the most common) and 3/16 inch. A wear indicator, in the form of a small notch in the bit tip, lets the tool operator know how much life is left in the bit.
Drilling through holes is another common HVAC application requiring the right hammer and bit combination. Core bits range in sizes, up to 6”. Typical core bits are 4-1/2 inch diameter, with diamond or carbide tips. A common example of a through-hole application is the core drilling required for installing PVC or cast pipes that extend between floors of a building. Adapter shanks for a variety of rotary hammers are available to accommodate core bits.
There’s more to drilling in concrete than meets the eye. Properly matching rotary hammers and bits to the application at hand will help ensure the speed, accuracy and productivity of installing HVAC equipment in concrete. But it’s important to keep in mind the style of bit you’re using and how it matches the anchor. Heating, cooling and other air movement systems are what drive quality of life in any building. Part of that quality of life is ensuring that equipment remains anchored properly and viable.
Michael Gerskovich is Group Product Manager-Accessories, Concrete Products, Robert Bosch Tool Corp.
Articles by Michael Gerskovich
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