How to Drill into Concrete - Bob Vila

How To: Drill Into Concrete

Bore a hole through masonry or concrete in a minute or less when you use this special tool and the correct technique.

How to Drill into Concrete with a Rotary Hammer

Photo: istockphoto.com

While concrete’s cool, industrial aesthetic is a go-to design touch in modern homes, its density and strength are what have long made it an attractive building material. That durability can be quite the obstacle, however, for homeowners trying to mount an art installation on a concrete feature wall, drill a hole to set a fence post at the end of the driveway, or sink a hole through the back corner of a concrete countertop. Such activities run the very real risk of damaging a drill bit or accidentally marring the concrete surface in an overzealous, poorly executed attempt at how to drill into concrete.

You can, in fact, drill a hole in a concrete interior feature wall armed with nothing more than your trusty rotary drill and a masonry bit—so long as you take care to not burn out the motor of the drill or demolish the bits. Older concrete, however, is often much more dense than some of the cosmetic concrete used in modern finishes, so boring through a 50-year-old concrete wall in your foundation with your old-school rotary drill just won’t cut it. When you’re working with older concrete—or if you’re planning to drill multiple holes about two to four inches deep and up to ¾ inch wide—it’s best to upgrade to an electric hammer drill.

Specially designed for drilling into masonry or rock using a rapid hammer action, these drills and their carbide-tipped masonry bits are widely available at tool rental shops. A quality hammer drill (also known as a rotary hammer) can bore a two-inch-deep, ¼-inch-wide hole in less than a minute, which is much faster than a rotary drill and thus justifies its roughly $40 afternoon rental cost. When renting or buying a hammer drill, look for one with good power, ideally more than one speed setting, a stop function, and an auxiliary handle for your spare hand for enhanced comfort, control, and safety.

MATERIALS AND TOOLS
– Pencil
– Ruler
– Hammer drill
– Masking tape (optional)
– Goggles
– Tungsten carbide masonry bits
– Large masonry nail (at least 3 inches)
– Hammer
– Canned compressed air
– Vacuum

How to Drill into Concrete

Photo: istockphoto.com

STEP 1
Mark the desired position of the holes in pencil on the concrete surface, and double-check their locations before you proceed. Also, during this planning and prep work, consider the drilling depth necessary for each hole. If your drill’s features include a stop bar, set it to the exact depth you want by following the drill manufacturer’s specifications. No stop bar feature? Instead, wrap a piece of masking tape around the drill bit to show you where to stop.

STEP 2
Don your goggles, then insert the appropriate tungsten carbide masonry drill bit for your desired hole size into the hammer drill. Next, get into position to drill by planting your feet firmly on the ground, shoulder-width apart. Hold your drill securely with both hands: Grip it in one hand like a handgun, and, if there’s no auxiliary handle for your spare hand, use that hand to brace the back of the drill.

It’s critical to control the drill so it doesn’t run away once you begin work. When you lean in to bore the hole, the drill bit should be perfectly perpendicular to the concrete. Be prepared for some recoil from the drill’s hammer action.

STEP 3
Make a guide hole first. Many hammer drills offer only two speeds, so turn your drill on at the slower speed for best control when making the guide hole. If your drill has only one speed, then work in short, controlled bursts of a few seconds each until you’ve established a hole. The guide hole needs to be just 1/8 to ¼ inch deep.

STEP 4
When you start with a guide hole at least 1/8 inch deep, your drill will be easier to control, but all the same continue to operate the drill with a steady, light-but-firm touch so you’re never forcing it in. If you’re feeling confident, turn the speed to full, keeping a firm grip on the tool with both hands, and drill into the concrete until the hole is complete.

Beware: Concrete can have air pockets and pebbles or stones that can make resistance unpredictable, with the result that it can be disturbingly easy to lose control of the tool for a moment.

STEP 5
If you hit obstructions, never force the drill farther into the concrete. This can damage the bits or drill, or cause you to lose control of the drill and mess up your hole, damage the concrete surface, or worse.

Whenever you reach any too-tough-to-crack spots that impede progress, set the drill down and grab the masonry nail and hammer. Put the tip of the masonry nail at the problem spot and give it a few taps—not hard whacks—with the hammer to break up the obstruction. When you’re done, resume drilling the concrete at a slow speed until you’re sure you’ve passed the rough patch.

STEP 6
Periodically pull the drill out to brush away concrete dust. Considering you can bore a two-inch hole in under a minute using a hammer drill, pausing every 15 to 20 seconds should suffice.

STEP 7
Once you have drilled your hole to the necessary depth, blow all of the concrete dust out of the hole with a can of compressed air then vacuum up whatever has fallen to the ground. You should still be wearing your goggles throughout this process in order to protect against any concrete dust and shards that might fly in your face and scratch your eyes.

STEP 8
Repeat this procedure for any other holes you need. Once through, a pass with a vacuum will make cleanup a breeze.




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