When drilling into a hard surface such as concrete or other masonry it is best to use a masonry drill bit. These bits cut by chipping and crushing the material rather than slicing it, with a tungsten-carbide tip bonded into a softened steel shank. That design lets the bit survive the abrasive, brittle, mineral-heavy structure of cured cement, mortar, brick, and block.
How a masonry bit actually removes material
Concrete is not a homogeneous solid. It is a composite of cement paste binding sand and gravel aggregate, and cured concrete typically carries a compressive strength in the range of roughly 2,500 to 6,000 psi for ordinary structural mixes. That strength comes from brittle mineral phases. A sharp-edges blade designed for wood or steel behaves badly here: it cannot shave a brittle matrix cleanly, and the abrasive silica wears a high-speed-steel edge dull within seconds.
A masonry bit answers this with geometry and hardness. The tip is a carbide insert, a sintered tungsten-carbide piece far harder than the aggregate it meets. The cutting head is wider than the fluted shank behind it, so the bit clears its own path. The flutes are relatively deep and open to carry powdered dust out of the hole rather than packing it tight.
The crucial mechanism is the drill mode, not just the bit. In hammer drilling, the bit is struck axially many times per second while rotating slowly. Each blow drives the carbide edge into the brittle matrix and fractures a small chip of aggregate and paste. Rotation indexes the edge to a fresh spot. The hole is made by cumulative brittle failure, not by cutting. That is why a masonry bit in a rotary-only drill often stalls or burns, and why a wood bit in hammer mode shatters.
Softness in the shank matters too. The steel body is tempered to absorb impact without snapping, while the carbide does the hard work. A bit that is too hard overall would chip or fracture under repeated blows. This division of labor, tough body plus hard tip, is the whole design principle.
Concrete numbers: speeds, sizes, and what the tool must supply
The numbers separate a working hole from a ruined bit. Hammer drilling is slow by design. Rotation speeds for masonry bits run far below wood or steel drilling, and larger diameters run slower still; a 1/4-inch hole and a 1-inch hole are different jobs, not the same job at different sizes.
Small diameters (about 3/16 to 5/16 inch): used for anchors and plugs, typically the fastest masonry drilling and the most forgiving on hammer energy. Mid diameters (about 3/8 to 1/2 inch): common for wedge anchors and conduit, where hammer energy and bit runout start to matter. Large diameters (about 5/8 inch and up): demand a rotary hammer with real impact energy; a light hammer drill will labor and overheat. Core bits (2 inches and larger): remove a ring of material rather than the full disc, for pipe and vent penetrations.
The tool must match the bit. A rotary hammer delivers impact through a piston mechanism and is built for sustained hammering. A hammer drill uses a smaller, faster-stroking mechanism and suits lighter work. Pushing a large masonry bit through old, hard concrete with an undersized tool converts impact energy into heat and vibration, which dulls carbide and can crack the tip. Depth also compounds difficulty: friction and dust clearing worsen as the hole deepens, so deep anchors need stepping and clearing rather than one continuous push.
Dust is a quantified problem, not a nuisance. The powder a masonry bit produces is fine and abrasive, and it packs the flutes if not cleared. Professionals pull the bit partly out periodically to let the flutes expel dust, and they avoid forcing. A packed flute stops cutting, generates heat, and glazes the carbide edge.
Edge cases where the standard answer bends
The keyword answer holds for cured masonry, but the edges are where thin guides fail. Rebar is the classic case. Reinforced concrete hides steel bars, and a carbide masonry bit will not cut steel efficiently; it will wander, dull, or bind. A bit that suddenly stops progressing and squeals has likely found rebar. The fix is relocation or a bit rated for both masonry and metal, not more force.
Brick and block are masonry but behave differently. Soft, hollow clay brick and lightweight concrete block drill quickly and can crumble or blow out the far side; too much hammer energy spalls the face. Hard fired brick and dense block sit closer to concrete. Mortar joints are the softest path in a brick wall and will accept a bit readily, but anchoring into mortar rather than brick sacrifices holding strength.
Old concrete is a separate regime. Concrete continues to cure and harden for years, and decades-old slabs can be markedly harder and more abrasive than fresh pours. Aggregate type matters: hard siliceous gravel resists the carbide more than soft limestone aggregate. A bit that drilled a new slab easily may struggle in a 40-year-old foundation.
Tile and stone sit at the far edge. Glazed ceramic and porcelain are brittle and chip; natural stone varies from soft to very hard. These often call for a small masonry or specialty bit at low hammer energy, or diamond tooling, and starting gently to avoid skating and cracking the surface.
Misconceptions that cost bits and time
The most common error is treating drill mode as optional. A masonry bit spun without hammering in concrete cuts poorly and overheats, because the brittle-fracture mechanism never engages. The second is using the wrong bit and blaming the tool: a wood or multipurpose bit in concrete dulls almost immediately.
Another misconception is that more pressure equals faster drilling. In masonry, excessive push force loads the tip, traps dust, and raises heat without increasing the fracture rate much. Steady moderate pressure with periodic clearing works better.
A subtler error is assuming all "masonry" bits are equal. Carbide tip size, braze quality, flute design, and shank type vary widely, and cheap bits lose the tip or dull early under sustained hammering. Professionals treat masonry bits as consumables and replace dull ones rather than grinding away with a spent edge.
The counterintuitive professional caveat: sharpness still matters. Many assume masonry bits cut purely by blunt impact and never need to be sharp. In practice a dulled carbide edge increases heat and vibration, slows progress, and can crack the tip, so experienced users retire dull bits earlier than beginners expect.
Practical actions and thresholds
Match the tool to the job before touching the wall. Use a rotary hammer for anything approaching 3/8 inch and up in concrete, and reserve light hammer drills for small holes and soft masonry. Confirm the drill is set to hammer mode for concrete.
Pick the bit by material and diameter. Standard masonry bit for concrete, brick, and block; a metal-capable bit when rebar is likely; diamond or specialty tooling for tile and hard stone. Choose a bit slightly larger than the anchor's nominal size only when the anchor specification calls for it.
Start the hole precisely. Mark the spot, use a punch or a small pilot to seat the tip, and begin at low speed to prevent skating. Then apply steady moderate pressure with hammering on, and clear dust every few seconds of drilling.
Watch for the warning signs and stop rather than force:
The bit stops progressing and squeals: probable rebar, relocate or switch bit type. Heavy smoke or a burning smell: too much speed, packed flutes, or wrong mode. The bit chatters and the hole enlarges: worn or bent bit, or too much hammer energy for the material. The surface spalls or cracks around the hole: reduce hammer energy, especially on tile and block faces. The tip looks blunted or chipped: replace the bit; continued use damages the tool and the hole.
Finish and clean the hole. Blow or vacuum dust out before anchoring, because dust left in the hole reduces anchor grip. Follow the anchor manufacturer's specified hole diameter and depth, since masonry anchoring strength depends heavily on those dimensions.
Limits of this guidance and a safety note
Masonry drilling advice cannot fully account for what is inside a wall. Embedded rebar, conduit, pipes, and post-tension cables are not visible from the surface, and hitting a post-tension tendon or live conduit is a genuine hazard. Structural concrete in particular may carry tensioned steel that must not be drilled. When the wall's composition is unknown, or the hole is structural, involve a qualified professional rather than drilling blind.
This article is general educational information about drilling tools and methods, not a construction, engineering, or safety plan for any specific wall or project. It does not replace inspection, engineering judgment, or the manufacturer's instructions for your drill, bit, and anchor. For structural work, unknown embedded services, or any doubt about what lies behind the surface, consult a qualified local contractor or engineer before drilling.