The technique of making holes in concrete is very useful and beneficial. You can install shelves, paintings, lamps, and so on more quickly and safely. The process itself is simple, but by choosing the right tool and understanding how it works, you'll save a lot of time.
Step
Part 1 of 2: Preparation Stage
Step 1. Buy or rent a good hammer drill
If you're only drilling 1-2 holes for a small project, a regular drill will suffice. However, drilling in concrete is easier to do with a hammer drill or rotary hammer for large projects. This tool cracks the concrete through rapid repeated shocks, then the drill will punch holes in the fractured material. If you use a regular rotary drill, the work will be slower and more difficult because the concrete layer is stronger than wood and metal. Buy or rent a hammer drill for tough jobs that go beyond just punching a few holes through cosmetic (nonstructural) concrete, such as the fine mix that is common on modern kitchen counters.
Usually, buying a more powerful hammer drill (at least 7-10 amperes) made by a trusted brand will be more profitable. Other advantageous features are speed adjustment, depth stop, comfortable grip and a second handle for everything else
Step 2. Get to know the tool
Read the user manual and learn about all the knobs and controls. Make sure you are comfortable with the tool before moving on to the next step.
- Follow all safety guidelines. This includes wearing safety goggles to protect the eyes from concrete debris, ear protection, and heavy gloves to protect hands from abrasion and hot drill bits. Respirators are also recommended for large projects that blow away a lot of dust.
- The hammer drill can be changed to a non-hammer drill setting by simply turning the collar.
Step 3. Insert a high quality rock drill bit
Carbide-tipped drill bits made for hammer drills (or labeled "rotary/percussive") are designed to withstand the impact and drilling forces of solid concrete. The flute of the drill bit should be at least as long as the hole to be drilled as it is important to remove dust from the hole.
- Rotary Hammer machines require a special drill bit, called SDS or SDS-MAX (for holes 1.5 cm in diameter) or Spline-Shank (for holes 2 cm or more).
- Reinforced concrete is much more difficult to punch holes if you want to drill deeper than steel reinforcement. Switch to the special rebar-cutting drill bit when the drill hits the metal. Slow down and stop occasionally to prevent overheating.
Step 4. Set the depth
Some drills have a depth setting or depth control bar. Read the user manual to learn how to use it. If the machine does not have depth control, measure and mark the required depth on the drill bit with a pencil or tape. If you don't know how deep the hole will be, follow these guidelines:
- Since concrete is a hard and dense material, a 2 inch (5 cm) screw is sufficient to hang light objects. Heavier projects require longer screws or concrete anchors, which state the minimum embedment on the package.
- Provide an additional 6 mm in the embedment as space for dust generated by the drilling process. You can reduce this length if you plan on removing the dust afterwards (described below).
- For concrete blocks or thin concrete surfaces, check the specifications for fasteners (bolts). Some plastic anchors require a solid back, and will fall off if drilled all the way across.
Step 5. Hold the drill properly
Grip the drill with one hand like a gun, with the index finger poised at the “trigger”. If the drill has a handle for the other hand, use it. Otherwise, put your other hand behind the drill.
Part 2 of 2: Drilling Concrete
Step 1. Mark the drilling points
Put a circle or a cross on the point on the wall where you want to punch holes with a pencil.
Step 2. Make a pilot hole
Attach the drill bit to the mark and drill briefly at low speed (if the tool has speed control) or in short bursts (if it doesn't have speed control). Make shallow holes (3-6 mm) to help guide the drill to the actual hole.
If the project requires a large diameter drill bit, consider using a small drill bit for the pilot hole. This step will increase the stability of the drill
Step 3. Continue drilling with more force
Turn on the hammer function if there is one. Insert the drill into the pilot hole, and keep it perpendicular to the concrete surface. Start drilling firmly pushing forward, but not forcing. Gradually increase the power and speed of the drill if needed, but make sure that the drill is steady and in control at all times. Concrete is not a homogeneous material, and drill bits can slip easily if they hit air pockets or gravel.
Press firmly enough to hold the drill in place, but don't force it forward (this will increase the wear of the drill bit, or even break it). You will learn to know the right amount of pressure through practice
Step 4. Pull the drill periodically
Slightly back off the drill and push it back every 10-20 seconds. This step helps draw the dust out of the hole.
- Stop the drill occasionally and pull it out for a few seconds to cool. This step is important, especially for rotary drills because it is easy to overheat during long drilling processes.
- You can feel a slight jump and jerk from the drill.
Step 5. Break the barriers using concrete nails
Sometimes, drilling results are not as expected. If you hit hard concrete, put a nail in the hole and hit with a hammer to break the concrete. Try not to hit the nail too deep to make it easier to remove. Insert the drill bit and continue drilling.
If you see sparks or metal, it looks like you hit the reinforcement. Immediately stop drilling and switch to the rebar-cutting drill bit until the resistance is broken
Step 6. Blow off the dust
Removing dust will increase the anchor strength of the concrete. Use a pipette or can of compressed air to blow the concrete dust out of the hole, then suck it up with a vacuum cleaner. Always wear safety glasses while working to protect against dust and debris.
- Concrete dust can be harmful if inhaled so be sure to wear a protective mask before working.
- You can also remove the dust using a damp cotton swab to wipe the dust in the hole.
Tips
- It's a good idea to have a second person hold the vacuum hose (or half a paper plate taped to the wall) just below the hole so that after-work cleaning is effortless.
- Screw in the mortar between the blocks, if possible. This makes it easier to drill holes in mortar than concrete blocks. Always use lead anchors to hold the screws in place if you are drilling in mortar as the screws attached to the mortar will loosen over time. For light weight tools (electronic case, conduit strap), plastic anchors (with ordinary screws) or "Tapcon" concrete screws (without anchors) are sufficient. Tapcon screws are easy to tell apart because they are blue in color. For other devices where the screws will bear the load (eg benches, railings or racks) strong lead anchors must be hammered in after holes have been drilled and screws inserted into the anchors.
- If the anchor rotates when installed, cut the plastic anchor into strips. Tap the strip into the anchor hole to secure it, then gently turn the screw by hand.
- Professionals use diamond core drill bits to drill holes larger in diameter than a rotary hammer can achieve. The use of a diamond drill bit depends on the characteristics of the concrete, including the size and hardness of the material, the length of time it takes to set, and whether the concrete is reinforced.
Warning
- The older the concrete, the more difficult it will be to drill.
- Do not press the drill as hard as possible. The drill bit can break.
- Some carbide-tipped drill bits can break when they touch water. If you plan to use water to help prevent overheating and reduce dust, read the product instructions and contact the drill bit manufacturer for a safer method. When using water, make sure the drill motor is not wet.
