Core drilling | Chalkline

Core drilling is the use of a hollow cylindrical bit faced with industrial diamonds to cut a round hole through concrete, reinforced concrete, masonry, brick, or natural stone. The bit removes a clean cylindrical plug (the core), leaving a smooth-walled hole sized to the bit. Standard residential bit sizes: 25 mm through 200 mm; specialist work goes much larger.

Where core drilling earns its keep on residential builds:

Slab penetrations for waste pipes, stormwater outlets, gas conduit risers.
Wall penetrations for HVAC duct, exhaust fan vent, sub-circuit conduit through brick or block.
Footing penetrations for under-house services where the design missed a sleeve.
Anchor preparation for chemical or epoxy anchors into existing concrete.
Specimen extraction for compressive-strength testing of an existing slab.

Sleeves cast in at the pour are always cheaper than core drilling later. Coring is the rectification path when sleeves were missed or design changes hit after the slab is down.

Wet vs dry coring. Two methods:

Wet coring is the residential default. Water is fed through the bit centre and out the kerf; the slurry captures dust and cools the diamonds. Slurry collection (a vacuum or a containment bund) protects the floor and stormwater.
Dry coring uses an on-tool dust-extraction system at the bit. Dry is acceptable only where wet is impractical (live electricals, finished floors). Even with extraction, dry coring releases more respirable crystalline silica (RCS) than wet.

Silica risk. Concrete coring is among the highest-RCS-generating tasks on a residential site. The Workplace Exposure Standard for RCS is 0.05 mg/m³ over an 8-hour shift. Dry coring without on-tool extraction can exceed that standard in minutes. Required controls:

Wet cutting as the primary engineering control, OR
On-tool dust extraction rated for RCS where wet is not possible.
P2 or P3 respirator regardless of which method.
Eye and ear protection (drills run noisy and slurry sprays).

Practical setup:

Mark the centre, drill a small pilot, then run the core bit slowly to bite.
Anchor the rig: most core drills bolt to the slab or wall with an expansion anchor or vacuum pad. A handheld core drill of 75 mm+ is unsafe.
Identify any embedded reo before coring. Cutting through structural reinforcement is a defect and may compromise the slab.
Plan slurry capture before the bit touches the substrate.

For builders. Outsource to a specialist coring contractor for anything over 50 mm or through structural concrete. The rig, training, and consumables (diamond bits at $300+ each) rarely make in-house coring economic unless it’s daily work.

Also known as: coring, diamond core drilling, wet core.

Category: WHS / silica / drilling / concrete.

Related

See also

Related articles