Drilling through concrete requires a hammer drill or rotary hammer, a carbide-tipped masonry bit, and steady technique. The job is straightforward once you match the right tool to the hole size you need and take a few precautions to protect yourself from silica dust. Here’s how to do it right, from tool selection through cleanup.
Pick the Right Drill for the Job
Two tools can drill concrete: a hammer drill and a rotary hammer. Both combine spinning with a rapid pounding action that breaks up concrete as the bit rotates, but they generate that pounding force in very different ways.
A hammer drill uses two ridged discs that slide past each other, causing the chuck to slam forward and back thousands of times per minute. It’s the more affordable option (starting around $50) and works well for holes up to about 1/2 inch in diameter. Most hammer drills double as a regular drill with the flip of a switch, making them a practical choice if you only need to drill a few small holes for anchors or screws.
A rotary hammer is a step up in every way. Instead of ridged discs, it uses a piston and crankshaft to create air pressure that drives the hammering mechanism. This delivers significantly more impact energy per blow, which means faster drilling and less fatigue. Rotary hammers also have three modes: drill only, hammer drill, and hammer only (turning the tool into a mini jackhammer for chiseling). If you’re drilling holes larger than 1/2 inch, drilling into reinforced concrete, or have more than a handful of holes to get through, a rotary hammer is worth the investment.
Choose the Right Bit
Standard twist bits won’t survive concrete. You need a masonry bit with a carbide tip, which is the hardened cutting edge brazed onto the end of the bit. For most home projects like mounting shelves, anchoring handrails, or setting tapcon screws, a carbide-tipped bit paired with a hammer drill handles the job.
If you’re working with reinforced concrete (concrete with steel rebar inside), carbide alone may not cut it. Diamond-tipped bits are the industry standard for reinforced concrete because they cut through both the concrete and the steel. A standard masonry bit will dull quickly or stall completely when it hits rebar.
Bit shanks matter too, especially for rotary hammers. SDS-Plus bits have a slotted shank (roughly the diameter of your pinky finger) that clicks into a keyless chuck and can handle holes up to 1-1/8 inches. SDS-Max bits have a thicker shank (closer to the diameter of your thumb) and are designed for larger combi hammers that hit harder, spinning at around 360 RPM with 2,800 blows per minute compared to the SDS-Plus drill’s typical 4,100 blows per minute at 750 RPM. The lower speed and higher impact energy of SDS-Max systems are built for bigger, deeper holes.
Protect Yourself From Silica Dust
Concrete contains crystalline silica, and drilling it creates a fine dust that’s dangerous to breathe. OSHA sets the permissible exposure limit at just 50 micrograms per cubic meter of air over an eight-hour period, with an action level of 25 micrograms. Those are tiny amounts. Even a single hole produces visible dust clouds that can exceed those thresholds in an enclosed space.
At minimum, wear an N95 respirator (or better, a P100) and safety glasses. OSHA specifically requires HEPA-filtered vacuums when cleaning drilled holes in concrete, and using one during drilling is even better. Many rotary hammers accept a dust-collection attachment that connects to a vacuum and captures dust right at the bit. If you’re drilling indoors, this isn’t optional for your health. HEPA filters capture 99.97% of particles down to 0.3 micrometers, which is the size range that matters for silica.
Hearing protection is also important. Hammer drills and rotary hammers are loud, especially in enclosed spaces where sound bounces off concrete walls and floors.
Mark and Start the Hole
Precise marking prevents wasted effort. Use a carpenter’s pencil or, better yet, place a piece of masking tape on the concrete and mark your point on the tape. The tape serves double duty: it gives you a visible target and helps prevent the bit from skating across the surface when you start drilling.
Begin at a low speed with light pressure. The goal for the first 1/4 inch or so is just to create a shallow guide hole that keeps the bit centered. Pushing too hard at the start causes the bit to wander. Once you have that shallow pilot dimple established, you can increase speed and pressure.
Drilling Technique That Works
After the pilot hole is set, increase to your working speed and apply firm, steady pressure. The key balance is this: too little pressure and the carbide cutting edges glaze over and stop biting, too much pressure and you risk overheating or damaging the bit. You want consistent forward force, not your full body weight.
If you’re unsure about speed, start on the lower end and increase gradually. For standard carbide masonry bits in a hammer drill, let the hammering action do most of the work. You’re guiding the tool, not forcing it.
Every 15 to 20 seconds of continuous drilling, pull the bit partway out of the hole while it’s still spinning. This clears concrete dust from the flutes (the spiral grooves along the bit) and prevents the bit from binding. Dust buildup is one of the most common reasons drilling suddenly slows to a crawl. If you notice the drill bogging down or the bit getting hot, back out, let things cool for a moment, and clear the hole.
For deeper holes, you may want to periodically blow out accumulated dust with a can of compressed air or a rubber bulb blower. Packed dust at the bottom of the hole acts as a cushion that absorbs the bit’s impact energy instead of letting it reach fresh concrete.
What to Do When You Hit Rebar
You’ll know immediately. The bit will suddenly stop advancing, and you may hear or feel a metallic scraping instead of the gritty grinding of concrete. If this happens, don’t force it.
The best approach is to avoid rebar entirely. A rebar scanner or basic metal detector, available at most hardware stores, can identify reinforcement locations before you drill. Even an inexpensive stud finder with a metal-detection mode can help. Move your hole location if possible, since cutting through structural reinforcement can compromise the concrete’s load-bearing capacity.
If you must drill through rebar, swap to a diamond-tipped bit rated for reinforced concrete, and reduce your drilling speed when you feel the bit contact steel. Standard carbide masonry bits are not designed to cut metal and will dull or chip rapidly against rebar.
Clean the Hole Before Installing Anchors
If you’re drilling holes for concrete anchors, especially adhesive anchors, hole cleanliness directly affects how much weight the anchor can hold. Residual concrete dust left in the hole prevents adhesive from bonding to the walls and can reduce anchor strength significantly.
The standard cleaning method is called “blow, brush, blow.” First, blow out loose dust using compressed air or a rubber bulb. Then scrub the inside walls of the hole with a round nylon brush sized to fit snugly. Finally, blow out the hole again to remove whatever the brush loosened. For adhesive anchors, the hole needs to be completely free of dust, debris, grease, and moisture.
Some newer hollow drill bit systems clean the hole during drilling by connecting to a vacuum, eliminating the need for separate cleaning. These work well in dry conditions but can clog when drilling in wet or saturated concrete.
Common Problems and Fixes
- Bit walks off the mark: Use masking tape on the surface and start with a slow-speed pilot hole. A center punch can also create a small dimple to seat the bit.
- Drilling slows to a stop: Pull the bit out and clear dust from the hole and flutes. Packed dust is almost always the cause.
- Bit overheats: You’re pushing too hard, running too fast, or both. Back off, let the bit cool, and reduce pressure. Some people mist the bit with water, which helps with cooling but creates silica-laden slurry that still needs respiratory protection.
- Hole is too shallow for the anchor: Drill 1/4 to 1/2 inch deeper than the anchor requires. Dust settles to the bottom and takes up space, and you want the anchor fully seated.
- Concrete crumbles or spalls around the hole: This usually means the concrete is old, low-density, or you’re too close to an edge. Move the hole at least 2 inches from any edge, and reduce hammering intensity if your tool allows it.