Diamond Core Drilling Glossary – UK Terms and Definitions

This glossary covers the terminology used in diamond core drilling and related structural concrete work. Terms are grouped by category: equipment, materials, methods, and regulatory. Each definition reflects standard UK trade usage.

Equipment Terms

Core drill motor: A dedicated rotary-only electric motor used to drive diamond core bits. Distinguished from SDS drills by the absence of a hammer function, a ½" BSP threaded chuck, and an internal water swivel for wet drilling. Power ratings: 1,200–2,500W for professional machines. See: diamond core drilling equipment guide.
½" BSP (British Standard Pipe): The standard thread specification used on core drill motor chucks and core bit arbors in the UK and Europe. BSP thread allows core bits to be threaded directly onto the machine spindle and provides the water-tight connection needed for the internal water feed in wet drilling applications.
Diamond core bit: A hollow cylindrical steel barrel with diamond-impregnated cutting segments welded to the open end. The bit rotates at speed against the material, grinding away a circular kerf and leaving a cylindrical core slug inside the barrel. Available in dry-rated (slotted/turbo barrel), wet-rated (solid barrel), and universal configurations. See: diamond core drill bits guide.
Segment: One of the diamond-impregnated blocks welded to the cutting end of a core bit barrel. Each segment contains industrial diamonds distributed through a metal bond matrix. As the bit rotates, the bond matrix wears progressively to expose fresh diamond cutting surfaces. Segment quality, bond hardness, and diamond concentration determine the bit's performance in a given material.
Bond matrix: The metallic alloy in which industrial diamonds are embedded in a core bit segment. Bond hardness determines how quickly the matrix wears: a soft bond wears quickly (used on hard, abrasive materials to constantly re-expose diamond); a hard bond wears slowly (used on soft materials to prevent premature segment loss). Mismatching bond hardness to material causes glazing (hard material, hard bond) or rapid segment wear (soft material, soft bond).
Glazing: Failure mode where a core bit stops cutting — the bond matrix wears smooth without releasing diamond, producing a polished, non-abrasive surface on the segment. Caused by using a hard-bond bit on hard, abrasive material, or by running a wet bit without water. A glazed bit can sometimes be recovered by dressing on soft abrasive material (sand-lime brick, aerated block). See: diamond core drill bit maintenance.
Motor-and-rig: A system combining a core drill motor with a rigid feed column and carriage that advances the motor and bit under controlled, steady load. The rig absorbs torque reaction and ensures perpendicular bit entry. Required for all precision-aligned holes and for any wet coring above approximately 107mm in concrete. Types: wall-mounted, vacuum-base floor rig, column-mounted for large diameter.
SDS adaptor: A device that converts an SDS Plus or SDS Max chuck on a standard drill to accept a standard core bit arbor. Allows dry core bits to be used on SDS drills for small diameters (up to approximately 50mm) in soft masonry. Not suitable for concrete or diameters above 50mm — SDS drills lack the sustained torque output and do not have an internal water feed for wet applications. See: SDS Plus vs SDS Max guide.
M-Class vacuum: A dust extraction vacuum rated to EN 60335-2-69 Class M, with filtration efficiency ≥99% at 0.3 microns — the medium hazard class covering respirable crystalline silica (RCS). The HSE specifies M-Class extraction as the minimum control for dry masonry drilling and chasing under COSHH 2002. A standard domestic or L-Class vacuum does not provide adequate filtration for silica-generating tasks. See: core drill dust extraction guide.
Dust shroud: A rubber or plastic enclosure that fits around the core bit or drill body and creates a sealed chamber at the cutting face, connected to the vacuum hose. Prevents dust generated at the cutting face from escaping into the surrounding air. The shroud must maintain contact with the wall surface throughout drilling to avoid bypass.
Pilot drill (centre bit): A small drill bit mounted at the centre of a core bit used to mark the hole position and prevent the core bit from walking across the surface on startup. Removed before the full depth of the cut is reached (the pilot hole depth is typically 20–30mm). Available in SDS and standard hex shank configurations.
Water swivel: A rotating seal on the core drill motor spindle or chuck that allows water to be supplied to the centre of the rotating bit without the feed hose twisting. Connects the machine's water inlet port to the hollow centre of the core bit barrel, routing water from an external supply through the bit to the cutting face.

Material Terms

Reinforced concrete (RC): Concrete containing embedded steel bars (rebar) or mesh designed to carry tensile loads that plain concrete cannot withstand. The standard structural material in UK commercial, industrial, and residential construction. Requires wet coring with a rebar-rated bit. Rebar positions must be located by ferroscan or GPR scan before drilling. See: reinforced concrete drilling services.
Post-tensioned (PT) concrete: Concrete in which high-tensile steel tendons are placed under active compressive load after the concrete has cured. The tendons are typically grouted into ducts cast within the slab or beam. Post-tensioned concrete is common in UK commercial office buildings, carparks, and flat-slab residential construction from the 1960s onwards. Cutting a PT tendon releases stored energy violently and can cause immediate structural failure — never drill PT concrete without GPR scanning and structural engineer sign-off. See: GPR scanning guide.
Respirable crystalline silica (RCS): The fine particle fraction of silica dust (particles below 10 microns aerodynamic diameter) generated when cutting, drilling, or grinding concrete, brick, stone, or mortar. RCS penetrates to the alveolar region of the lungs and causes silicosis, lung cancer, and COPD. The HSE Workplace Exposure Limit (WEL) is 0.1 mg/m³ (8-hour TWA). Control requires wet drilling for concrete or M-Class extraction for dry masonry work. See: silica dust control in UK construction.
Aerated concrete (Aircrete): A lightweight cellular concrete product manufactured with aluminium powder to create uniform air voids. Sold under trade names including Thermalite, Celcon, and Durox. Compressive strength 2.5–7.5 MPa — far lower than structural concrete. Used for non-structural internal leaf blockwork in UK domestic and light commercial construction. Drills with a dry hard-bond bit at low feed pressure; cuts quickly.
No-fines concrete: Concrete made with coarse aggregate only — no sand filler — giving it an open, porous texture. Used in some UK post-war housing for external walls. The coarse aggregate texture means a core bit may intermittently lose bite at aggregate boundaries. Adjust feed pressure to maintain consistent cutting contact.
Rebar: Reinforcing bar — deformed steel bar embedded in reinforced concrete to carry tensile loads. Common sizes in UK structural concrete: H8–H32 (diameter in mm). Rebar positions must be identified by ferroscan or GPR scanning before drilling. Striking rebar with a non-rated bit damages the bit and may damage the structural element. See: drilling through rebar guide.
Soft bond / hard bond: Descriptors for diamond core bit segment bond matrix hardness. Soft bond: for hard, dense, abrasive materials (structural concrete, engineering brick, granite). Hard bond: for soft, non-abrasive materials (standard brick, blockwork, aerated concrete). Medium bond covers intermediate materials (standard commercial concrete C25–C30, mixed substrates).
Engineering brick: A dense, low-absorption fired brick manufactured to Class A or Class B specification. Used in construction where high compressive strength, durability, or water resistance is required — civil engineering structures, retaining walls, below-ground masonry. Significantly harder than standard facing or common brick. Requires a wet-rated or universal core bit; dry-only hard-bond bits glaze or wear rapidly on engineering brick above approximately 65mm diameter.

Method Terms

Wet drilling: Diamond core drilling using a continuous water supply fed to the cutting face via the machine's internal water feed. Water cools the segments, suppresses silica dust at source, and flushes debris clear of the cutting face. Required for all concrete, reinforced concrete, and hard masonry. See: wet core drilling services.
Dry drilling: Diamond core drilling using a dry-rated (slotted or turbo barrel) core bit without water. Air circulation through the barrel slots cools the segments. Correct for brick, blockwork, and aerated concrete. M-Class dust extraction required. See: dry core drilling services.
Stitch drilling: A technique that creates a large opening by drilling a series of overlapping circular core holes in sequence. Adjacent cores share a tangent line; the remaining web between holes is removed by chisel or secondary cutting to produce a combined opening. Used where the required opening exceeds single core bit diameter, saw cutting is impractical, or a non-rectangular geometry is needed. Structural engineer approval required.
Wall chasing: Cutting a narrow rectangular channel into the face of a masonry wall to allow conduit, pipework, or cable to be buried flush with the wall surface. Carried out with a diamond wall chaser (two parallel blades on a fixed-depth guard) or an angle grinder (inferior — more dust, less accurate). M-Class dust extraction required. Depth limits apply in load-bearing walls under Building Regs Approved Document A. See: wall chasing services.
Wall sawing: Diamond cutting using a track-mounted circular blade to produce straight cuts in vertical concrete walls. Used for door and window openings, structural alterations, and large rectangular penetrations. Maximum single-pass depth approximately 450mm. Structural engineer approval required before cutting load-bearing elements. See: diamond saw cutting services.
Floor sawing: Diamond cutting using a self-propelled saw with a downward-facing blade to produce straight horizontal cuts in concrete slabs. Used for control joint cutting, slab removal, and service trench cutting. Generates alkaline slurry — environmental containment required. See: diamond saw cutting services.
Core slug: The cylindrical plug of material removed from inside the core bit during drilling. The slug forms within the hollow barrel and is ejected or pushed out on completion of the hole. In dry drilling through brick, the slug typically remains in the barrel and is removed with a core ejector or screwdriver through the barrel slots.

Regulatory Terms

COSHH (Control of Substances Hazardous to Health Regulations 2002): UK regulations requiring employers to assess and control exposure to hazardous substances including RCS dust. Sets the legal framework for dust control in drilling and cutting operations. Requires that exposure is reduced to as low as reasonably practicable — wet drilling for concrete, M-Class extraction for dry masonry. See: health and safety in diamond core drilling.
CDM 2015 (Construction Design and Management Regulations 2015): UK regulations governing health and safety management in construction. Imposes duties on clients, principal designers, principal contractors, and contractors. On notifiable projects, structural concrete drilling must be addressed in the pre-construction health and safety plan. Applies to all construction work regardless of scale. See: core drilling permits and regulations.
Workplace Exposure Limit (WEL): The maximum concentration of an airborne substance to which a worker may be exposed over a defined period without adverse health effect. The WEL for respirable crystalline silica is 0.1 mg/m³ (8-hour time-weighted average). Set by the HSE under COSHH regulations.
GPR (Ground Penetrating Radar): A scanning technique that transmits radar pulses into concrete and records reflections from internal features — rebar, PT ducts, conduits, and voids. Mandatory before drilling any structural concrete where post-tensioning cannot be confirmed absent. The only scanning method that reliably detects both conventional reinforcement and grouted PT tendons. See: GPR scanning guide.
Ferroscan: An electromagnetic induction scanning tool that locates metallic reinforcement in concrete and measures cover depth. Faster than GPR for straightforward rebar mapping. Cannot reliably detect grouted post-tensioned tendons — use only where PT has been confirmed absent by structural drawings.
PAS 128: UK specification for underground utility detection surveys. Defines survey quality levels from D (desk study) to A (field investigation with intrusive verification). PAS 128 Level B or A scanning is required on highway and infrastructure projects before drilling to locate buried utility services. See: core drilling for utility contractors.
NRSWA (New Roads and Street Works Act 1990): UK legislation governing works in the public highway. Any core drilling or cutting in the public highway (including footways and carriageways) requires a Section 50 licence (for non-statutory undertakers) or S55 notice (for statutory undertakers), traffic management compliance, and reinstatement to the authority's specification. See: core drilling for utility contractors.
CIS36: HSE Construction Information Sheet 36 — guidance on controlling dust from masonry work including drilling, cutting, chasing, and grinding. Specifies M-Class vacuum extraction as the minimum control for tasks generating RCS above the WEL. Widely referenced by contractors and principal contractors as the benchmark for COSHH compliance on masonry work.
WEL: See Workplace Exposure Limit.