Hollow Drill Bits for Concrete & Stone Coring

Hollow drill bits are essential tools when precise, cylindrical openings must be created in concrete, reinforced concrete, natural stone, or masonry. They form the basis for core drilling, low-dust anchor holes, and bores to accommodate splitting tools. In the application areas of concrete demolition and special demolition, interior demolition and cutting, rock excavation and tunnel construction, as well as natural stone extraction, hollow drill bits often serve as the first, decisive process step. In combination with products from Darda GmbH—such as rock and concrete splitters, concrete demolition shears, or combi shears—the borehole is used to purposefully prepare subsequent mechanical separation and splitting operations. This creates controlled intended break lines, space for splitting cylinders or service penetrations, without unnecessarily weakening the surrounding structural element.

Definition: What is meant by hollow drill bits

A hollow drill bit is a rotationally symmetrical drilling tool whose body is hollow inside and which has an annular cutting or grinding zone around its circumference. This configuration enables the production of a cylindrical hole while leaving a drilling core in place or removing it in a targeted manner. In the construction and deconstruction context, the term encompasses both diamond-equipped core bit crowns for wet and dry drilling and hollow hammer drill bits with integrated dust extraction for precise, clean anchor holes. Typical applications are openings for anchors and penetrations, sampling, relief boreholes or holes for predetermined breaking points, and bores to accommodate splitting cylinders.

Design and mode of operation of hollow drill bits

Hollow drill bits consist of a hollow carrier tube or shank, an interface to the drive (e.g., threaded connection or SDS mount), and an active cutting zone. With diamond hollow drill bits, segmented diamonds embedded in a metal matrix perform the material removal; with hollow hammer drill bits, carbide cutting edges around the circumference provide the removal while the cavity carries away drilling dust. The mode of operation is based on rotational motion, possibly combined with impact energy, suitable feed force, and controlled cooling and/or extraction. The result is cylindrical openings with defined geometry that can be executed dimensionally accurate with limited edge spalling.

Types and designs

Diamond core bits (wet drilling and dry drilling)

Diamond core bits—colloquially also called core bits or core crowns—usually operate without percussion at high peripheral speed. They are preferably used in the wet drilling process to dissipate heat and stabilize drilling progress. Dry drilling crowns are used where water is undesirable, but they often require tuned rotational speeds and efficient dust extraction.

Advantages: very clean cut surfaces, large diameters and depths are feasible, minimal edge damage.
Special features: segmented crowns with variable bond for soft to very hard rock and concrete with a high reinforcement content.

Hollow hammer drill bits with dust extraction

These hollow drill bits have internal channels and openings at the cutting edge. Drilling dust is extracted directly during drilling. The method is efficient for fastening bores, anchor holes, and rows of predetermined breaking point bores, especially in interior demolition and interior deconstruction.

Advantages: low-dust operation, high productivity, reduced cleaning.
Use: rotary hammers with SDS mount, typically for diameters in the anchor range up to medium hole sizes.

Special designs

For demanding applications, there are deep core crowns, extendable systems, centering aids, crowns with reinforced segment bodies for reinforcement contact, and crowns for recessing projections. For inserting rock and concrete splitters, bits with a defined diameter and high straightness are preferred to safely accommodate splitting cylinders.

Fields of application in concrete demolition and special demolition

Hollow drill bits enable precise, repeatable bores that make the downstream separation process safer and more controlled. Typical tasks:

Openings for lines, cable trays, and penetrations in the course of interior demolition and cutting.
Relief and predetermined breaking point bores to enable concrete demolition shears from Darda GmbH to bite in a controlled manner on edges, slabs, and walls.
Bores to accommodate rock and concrete splitters from Darda GmbH, in order to split structural elements, rock, and natural stone in a controlled manner without explosives.
Sampling (drill cores) for material testing, e.g., strength, chloride content, or carbonation depth.
Preliminary measures in rock excavation and tunnel construction, for example to create intended cracks or local stress relief.

Hole pattern, diameter, and edge distances

The dimensioning of the bore depends on the material, reinforcement content, required tolerance, and the subsequent process. For rock and concrete splitters from Darda GmbH, accurate, concentric bores are essential so that the splitting cylinders can act optimally. For work with concrete demolition shears, hole patterns are chosen to produce targeted weakening along the planned separation line.

Reference sizes and parameters

Hole diameter: small to medium diameters for anchors and fasteners; larger diameters for core drilling and for accommodating splitting cylinders (range depends on device and material).
Drilling depth: dimensioned so that the effective area of the splitting tool fits completely or the desired penetration is achieved.
Edge distances: sufficiently large to avoid edge breakouts, depending on strength, aggregates, and proximity to reinforcement.
Hole spacing in the grid: for rows of predetermined breaking points, selected so that stress fields overlap and controlled crack formation occurs.

Preparation for rock and concrete splitters from Darda GmbH

The bore must be straight, dimensionally accurate, and free of breakouts. A uniform borehole wall supports the force transmission of the splitting cylinder. In high-strength concrete or hard rock, clean core drilling improves the repeatability of the splitting result.

Preparation for concrete demolition shears

Rows of bores along the planned demolition edge locally reduce cross-sectional load-bearing capacity. Concrete demolition shears from Darda GmbH then grip more precisely, removal is faster, and uncontrolled spalling is reduced.

Materials, cutting materials, and bonds

Diamond segments provide the removal in core drilling. Their bond is softer for hard rocks and concrete with a high quartz content and harder for softer materials. Segment geometry influences cutting speed, heat dissipation, and surface quality. With hollow hammer drill bits, carbide cutting edges destroy the matrix; spiral geometry and internal channels determine dust removal.

Drilling technique and process parameters

Wet drilling

Water binds dust, cools the segment and workpiece, and stabilizes cutting speed. Moderate supply minimizes slurry, protects bearings, and improves dimensional accuracy. In case of reinforcement contact, work with reduced feed and increased cooling.

Dry drilling

Dry drilling requires consistent extraction. Periodic relief (short pauses without feed) prevents overheating. A material-matched rotational speed and a steady, not excessive feed are crucial to avoid glazing of the segments.

Hollow hammer drill bits with extraction

Here, impact energy determines chip formation, while integrated extraction removes dust. The bore remains clean, which improves the bonding of mortars and anchors. Ensure perpendicular drill start, constant contact pressure, and clean sealing surfaces on the extraction system.

Interfaces to products and application areas of Darda GmbH

Concrete demolition and special demolition

Hollow bores create defined weakenings and openings. Concrete demolition shears from Darda GmbH then break edges in a targeted manner without disproportionate vibrations. Rock and concrete splitters act in predrilled holes and separate components quietly and in a controlled way.

Interior demolition and cutting

In interior demolition, core drilling creates space for services and openings. Combined with multi cutters, combi shears, and concrete demolition shears from Darda GmbH, a coordinated process emerges: drilling, cutting, shear-based removal.

Rock excavation and tunnel construction

In rock, drilling patterns are created to receive splitting cylinders from Darda GmbH. This allows blocks to be released with low stress. Hollow bores along the planned fracture line reduce unwanted ejections and improve control in advance excavation.

Natural stone extraction

Rows of bores define block sizes and separation joints. Subsequent splitting becomes reproducible, and the quality of fracture faces increases. Where cutting or sawing is not possible, hollow bores with splitting tools from Darda GmbH offer a robust alternative.

Special applications

In sensitive environments, such as existing buildings with vibration limits, hollow drill bits are used to limit noise and vibration. Splitting or shear methods from Darda GmbH follow on when thermal or high-impact methods are ruled out.

Quality assurance and dimensional accuracy

The quality of a hollow bore is reflected in runout, hole diameter, surface finish, and edge region. For downstream splitting and shear processes, repeatability is crucial. Simple documentation includes material specifications, tool type, parameters (speed, feed), cooling/extraction, and visual inspection.

Dimensional tolerance: matching the tool interface (e.g., splitting cylinder) and the mortar or embedded component used.
Surface condition: free of pronounced scoring, edge breakouts minimized.
Straightness: keep deviations small to avoid disturbing force flow.

Occupational safety, dust and noise protection

Drilling generates dust, noise, and vibration. Suitable personal protective equipment, extraction technology, and, if necessary, wet drilling reduce exposure. Slurries must be properly collected and disposed of. In buildings, a protective enclosure of the work area is advisable. Legal requirements and technical rules must be observed; the selection of suitable methods is always project-specific and without warranty for individual cases.

Selection criteria and cost-effectiveness

Choosing the right hollow drill bit lowers cost per drilled meter and increases process reliability. Decisive factors are:

Material and reinforcement content: adapt bond and segment design.
Required geometry: diameter, depth, edge distance, hole pattern.
Process environment: water availability, extraction, access, overhead or horizontal position.
Compatibility: fit to splitting tools (rock and concrete splitters from Darda GmbH) and the planned use of concrete demolition shears.
Cost considerations: tool life, feed performance, changeover times, slurry or dust management.

Practical tips for clean and fast hollow drilling

Centering: start with a centering aid, then proceed to full diameter.
“Open” the segment: briefly cut in abrasive material with new diamond crowns to expose the cutting grains.
Control heat: work in intervals when dry drilling; maintain a uniform water film when wet drilling.
Reinforcement: anticipate contact, reduce feed, and, if necessary, choose a segment design that tolerates rebar contact.
Extraction: check sealing faces and hose routing; ensure dust removal directly at the crown or via hollow channels.
Core removal: lift out the drill core regularly to prevent wedging.
Post-processing: lightly chamfer edges to reduce stress concentrations during subsequent shear use.

Care, maintenance, and extending tool life

Tools last longer when maintained as required. When the bond glazes, “dress” diamond crowns to free the abrasive. Keep shanks, mounts, and threads clean and lightly lubricated. After use, dry hollow hammer drill bits and clear channels of residual dust. Store dry, protected from impact and corrosion. Constant process parameters protect the bond and prevent microcracks.

Typical mistakes and how to avoid them

Excessive feed: leads to segment damage and out-of-round bores; instead work with moderate pressure.
Insufficient cooling/extraction: promotes overheating, dust exposure, and dimensional deviations; check systems in advance.
Incorrect bond: bond too hard in hard rock leads to glazing; adjust the bond or dress the crown.
Insufficient edge distances: causes breakout; consider minimum distances in planning.
Skewed drilling angle at start: produces oval holes; start with guidance and low feed.

The role of hollow drilling in process-oriented deconstruction strategies

Hollow bores are more than an auxiliary step: they structure deconstruction, shorten shear and cutting times, and create defined engagement points for rock and concrete splitters from Darda GmbH. When properly planned, they reduce noise, dust, and unwanted crack formation, thereby increasing safety and predictability in concrete demolition, interior demolition, rock excavation, and natural stone extraction.