Take the work out of drilling concrete

Take the work out of drilling concrete

The right tool and the right approach can make anchor installation easier

As power tool manufacturers squeeze more power into and out of new hammer drill and rotary hammer models, drilling holes in concrete for anchor installation should get easier. However, tool experts agree that contractors often use the wrong tool for the job. “We often see contractors using a too small tool for the job. We see users drilling a series of 3/4" or 1" anchor holes overhead using a 7/8" hammer drill on a lift. This is taxing the user and the hammer to the maximum with too much vibration and stress,” says Spencer Maid, director of corded products at Milwaukee Electric Tool.

Hammer drills are small, utility tools best reserved for holes 3/8" or smaller in concrete block or brick, the experts agree.

“Generally speaking, hammer drills are better for drilling smaller holes in softer materials compared to rotary hammers, Hammer drills should be used when drilling 1/4" and smaller holes in concrete or 1/2" or smaller holes in brick or block. The optimum hole size range for an SDS hammer is 3/16" to 5/8" holes in concrete,” says Jon Goebel, DeWalt rotary hammer product manager. For holes ranging from 5/8" to 3/4", the experts recommend using SDS or SDS-Plus drills and SDS-Max or spline bits and rotary hammers for 3/4" to 1 1/2" holes.

“Evaluate the job before selecting the tool. What diameter and depth of holes are you drilling? How many holes? Is it reinforced concrete? Answering these questions will help you select the proper drill motor. SDS-Plus bits are by far the most popular due to their availability, price, size range and drill motor popularity,” says Patrick Kearl, Relton national sales manager.

A variety of handle configurations are available. “Most rotary hammers in the United States feature L-handle or D-handle grips. D-handles are good for overhead and into-floor drilling because they offer better arm extension and better comfort. The pistol grip is more popular in Europe, the Middle East and China. They are all-purpose tools, especially for horizontal drilling,” says Maid.

Making the hole
Concrete drilling/anchor installation experts offer the following tips that can help users make accurate holes productively and safely:

Read the directions. Always read the product installation instructions and don’t take shortcuts. “Fasteners are designed to meet performance criteria, but they can’t if they are installed incorrectly,” says Dan Harmon, anchor systems engineer for Simpson Strong-Tie. “The instructions are very specific about hole drilling and preparation and should be followed to the letter. With adhesive anchors, hole cleanliness is very important; with mechanical anchors, torquing them to the right level is critical,” he says.

Know what you’re drilling. “Don’t drill holes into concrete without knowing what might be embedded in there. There may be conduit, rebar, or electrical wires embedded in the aggregate, says Goebel.

If your drilling job takes you into a jungle of rebar, then you have little chance of being able to work around it. “If it’s there and you need a hole where it is, you must use a rotary-only drill bit such as Relton’s Rebar Cutter,” says Kearl. Trying to cut through rebar with a carbide bit will only ruin the bit.

Wear personal protective equipment (PPE). Concrete dust and noise create hazards, so the experts suggest controlling dust with extraction systems or wearing respiratory protection. “DeWalt offers add-on dust extraction units that protect the operator from dust and debris, especially in overhead drilling,” says Goebel. Otherwise, wear respiratory protection. Also, always use eye and hearing protection, the experts advise.

Use a good bit. Bits wear over time, and can even wear to the point where they can’t make the correct size of hole. “Check your drill bit’s tolerance,” says Jason Wagner, director of mechanical anchoring at Powers Fasteners. “It should meet ANSI B212.15, which is a standard for carbide bit tolerances in concrete and masonry. Use a vernier caliper to check for wear.

Powers quantifies bit life in number of linear feet drilled. “We suggest replacing a 3/8" SDS bit after drilling the equivalent of 35' of holes and a 7/8" SDS bit after 110' of holes. The best gauge is the operator feeling the bit isn’t performing as it should. You will feel it before you see it,” says Wagner.

Warm up the tool. When beginning in the morning, warm the rotary hammer up to get optimal performance. “Drill a couple of holes to effectively warm up the tool,” says Goebel.

Use two hands. “Always use the side handle that’s provided with the rotary hammer or hammer drill for better tool control. Keep two hands on the tool,” says Goebel.

Don’t make the work harder. If you are drilling into the floor, the weight of the drill should do the work. Too much weight on the drill actually negates its force and transmits the power back through the operator. “The impact energy comes back through the user. It’s wasted energy to push down on the tool. If you apply too much pressure, the bit can even bind in the hole. Too much pressure could cause the hole to take twice as long to drill.

“In hard aggregate, the instinct is to push down harder, but it’s better to pull the bit out a bit and clean debris out of the flutes and then go back into the hole so the bit can do its work,” Wagner says.

Remain perpendicular. Wagner suggests keeping the bit perpendicular to the surface. “This helps the drill bit’s cutting edge pull it into the hole,” he says.

A drill stand can also help assure straight holes. “Otherwise, align your body with the drill and physically feel the balance of the tool on the drill tip. You can feel it if it’s not level. You’ll feel a resistance or a rub in the side of the hole if the drill is not straight,” says Wagner.

Harmon suggests asking a co-worker to act as a spotter for the drill operator, especially in horizontal drilling jobs. “The straighter the hole the better. A spotter might be a good idea to check drilling angle from two directions to assure you are as close to 90 degrees as possible to the drilling surface. A hole that’s not at 90 degrees could affect anchor performance and fastener and hanger fit. Two people may sound like overkill, but it can save time later,” he says.

Clean the hole thoroughly. Although not as important in overhead drilling, some users will over-drill a hole instead of properly cleaning the hole to the manufacturer’s specification.

“This is incorrect, especially with adhesive anchors. Follow the anchor manufacturer’s specific hole-cleaning directions for proper anchor performance. Never take short cuts,” Wagner says.

Keep your bits sharp. While some are being used, have others sharpened. “You can also keep heat down by rotating in fresh bits if drilling is constant so they have a chance to cool. Heat is a killer of cutting tools,” says Kearl.

Good vibrations?

For years, vibration simply came with the territory of making holes in concrete. Hammer drills and rotary hammers can create hand- and arm-numbing sensations that, until recently, were tolerated.

But that’s changing, tool experts report, as Europe and other international groups regulate vibration produced by tools and equipment. There is no aggressive movement afoot in the United States for similar regulations, but the international rule-making effort will bring about tool designs that cut vibration transmission to end-users in the United States.

“The future holds even greater vibration reduction in these types of tools,” says Spencer Maid, director of corded products at Milwaukee Electric Tool. “This is driven by Europe’s tighter standards that require independent testing groups to measure tool vibration transmission, which in turn mandates how long the user can use that tool per day. It’s an effort to reduce white finger or white glove disease, which describes tissue damage from vibration exposure. If you decrease vibration, workers can make more holes or chip longer every day,” he says.

Power tools are an international market, so the European legislation is also driving tool design in the United States, says Jon Goebel, DeWalt rotary hammer product manager. "We always keep a close eye on the regulations affecting power tool use that are evolving in Europe because there is a strong likelihood that these same standards will make their way over to the United States.”

Published in the July/August 2008 issue of Contractor Tools and Supplies magazine.

back to concrete archives