How To Drill Holes In Concrete

The ability to drill holes in concrete is a useful and convenient skill. With it, you can easily hang shelves and pictures, install lamps, and do a lot of housework quickly and safely. The process of drilling concrete is quite simple, but with the right selection of tools and understanding of the principles of work, you will save a lot of time.

Preparations

Buy or rent an impact drill.

According to mechanicfaq.com, drilling holes in the concrete is easier with an impact drill or a rotary hammer. These tools will allow you to crush the concrete with reciprocating strokes and remove the resulting chips by rotating the drill. Working with a normal drill will be slow and difficult, as concrete is not drilled as easily as wood or metal. It’s better to pay a little more and rent percussion tools if you have something more extensive than drilling a few holes in decorative (rather than structural) concrete surfaces.

When buying a tool, it’s usually reasonable to pay a little more for a more powerful hammer of a well-known brand. Other useful parameters to consider include the adjustable speed of rotation, adjustable drilling depth, ease of gripping the tool, and the presence of a second handle.

Learn about the tool.

Read the user’s manual and note what all the buttons and switches on the tool are for. You should be familiar with how to use the tool before proceeding to the next step.

Follow safety precautions. This includes wearing safety goggles to keep the concrete chips out of your eyes, using earplugs to protect your ears, and wearing thick work gloves to protect your hands from friction and hot drills. A respirator is also recommended for long-lasting work that generates a lot of dust.

Use a concrete drill bit  of high quality.

Concrete drills with tungsten carbide tips (or, as may be indicated on the package, “impact drills bits”) are specifically designed for impact drills and can withstand hard concrete. The length of the working part of the drill with grooves should be no less than the depth of the hole you are going to drill. These grooves are important for extracting the dust from the hole.

For rotary hammers, you should use special drill bits or so-called drill bits with SDS or SDS-MAX markings (for drilling holes up to 0.4 inches in diameter) or piercing drills (for holes with 0.8 inches in diameter and more).

Reinforced concrete is much harder to drill if the depth of the hole must be greater than the depth of the steel rebar in the concrete. As soon as the concrete drill bit reaches the rebar, replace it with a metal drill bit. During the process, slow down and stop from time to time to prevent the drill bit from overheating.

Adjust the drilling depth.

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Some drills have the option of setting the drilling depth or a special limiter. Read the user’s manual for the tool to learn how to use it. If your instrument is not equipped with a drilling depth limiter, measure and mark the desired hole depth on the drill bit with a pencil or masking tape. If you’re not sure how deep the holes you want to drill, follow the recommendations below:

As the concrete is a hard and dense material, the 0.9 inches deep holes will be enough to fix the screws to the wall on the wall plugs for hanging light objects. Heavier items will require longer screws with dowels or even anchors, the minimum depth of which must be indicated on the packaging.

Increase the depth of the hole you need by 5 mm so that there is room for the dust residue from drilling. This is not necessary if you are going to clean the hole from dust afterward.

When working with hollow concrete blocks or thin concrete surfaces, be sure to read the instructions for the fasteners. Some plastic anchors require strong support along the entire length as may simply fall out if inserted into a through-hole on a thin wall.

Get the drill right.

Hold the drill with one hand like a gun, with your index finger on the start button. If the drill is equipped with an additional handle, grip it with the other hand and use it to hold the tool more securely. Otherwise, simply pick up the drill with the other hand from below and closer to the back.

Concrete drilling

Mark the spot to drill the hole.

Using a soft pencil, mark a point or a cross on the wall where you want to drill a hole.

Drill a marking hole.

Place your drill against the mark and run it for a short time at a slow speed (if it’s adjustable) or press the start button briefly (if there is no speed adjustment). You should have a 3-6 mm recess that will help you guide the machine correctly when drilling the main hole.

If you will need a large diameter drill, consider using a smaller diameter drill bit for the marking hole. This way you can increase the stability of the drill during further work.

Keep drilling, but longer.

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Switch to percussion mode (if your drill has one). Place the drill on the marking hole strictly perpendicular to the concrete surface. Start drilling again with steady but not excessive pressure, so that the drill is immersed in concrete. Gradually increase the drill’s speed of rotation and pressure if necessary, but keep in mind that the drill should remain under your full control and in a stable position at all times. Concrete is rather uneven, and the drill can easily slip if caught in an air pocket or void.

Put enough pressure on the drill to keep it in position, but don’t push it too far forward (this will increase wear of the drill and may cause it to break). You will learn from your own practical experience how to press the drill firmly.

Remove the drill from the hole from time to time.

Pull the drill back a little bit every 10-20 seconds and push it back into the hole. This helps to get rid of accumulated dust.

Turn off the drill and remove it from the hole from time to time, so that the tool can cool down for a few seconds. This is especially important for conventional drills without impact function, as they are easily overheated if used for a long time.

Use a concrete chisel to go through particularly hard obstacles.

Sometimes, the drilling process doesn’t go as expected. If you come across a particularly hard section of concrete, put a pointed concrete chisel in the hole and tap it with a hammer to crush the concrete in that place. Be careful and don’t hammer the chisel too far, or it will be difficult to remove it. Then insert the drill bit  into the hole again and continue drilling.

If you notice sparks or see metal in the hole, this is rebar. Stop work immediately and use the metal drill until you pass through a metal barrier.

Blow the dust out of the hole.

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Removing dust from the hole increases the security of the anchors in the concrete. Use a rubber blower or compressed air can to blow the dust out of the hole and then vacuum it. When you blow out the dust, don’t take off your safety goggles to prevent it from getting in your eyes.

Useful tips

If someone holds a running vacuum cleaner hose (or half a paper plate glued to the wall) underneath the hole, you will save time on the cleaning afterward.

Try to make holes in the mortar at the junction of the concrete blocks, as the mortar is easier to drill than concrete. If you have made holes in the mortar, be sure to use metal anchors for screws, as the screws without anchors will loosen and fall out very quickly.

However, for some lightweight equipment (like. junction boxes and wire clamps), it’s okay to use plastic dowels (with conventional screws) or concrete screws (without anchors and dowels). In other cases, when the screws carry a certain load (to hold stands, handrails, or shelves), it’s necessary to hammer strong metal anchors into the screw holes and only then tighten the screws.

NB

The older the concrete, the harder it is to drill.

Don’t put all your weight on the drill. You can break the drill this way.

Some carbide drills may break down if you decide to cool them down with water. If you decide to use water against overheating or to reduce the amount of dust during operation, first read the instructions for the drills or consult the manufacturer. Be careful when using water and make sure that it doesn’t fall on the drill motor (learn more).

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