There is no single best core drilling method — there is only the correct method for the specific hole size, material, and use case. A plumber drilling a single 107mm boiler flue hole once a month and a contractor drilling twenty 150mm floor cores in reinforced concrete need completely different setups. This guide sets out the three main methods, their limits, and which applications each suits.
Core Drilling Methods at a Glance
- Dedicated core drill machine: the professional standard — handles all diameters, all materials, wet and dry
- SDS adaptor with diamond bit: rotation-only on an existing SDS drill — suitable up to 52mm in soft masonry only
- SDS hammer with TCT core bit: hammer-drill mode — for occasional domestic use in standard brick and block only
- Wet coring (dedicated machine + wet bit): required for concrete and reinforced concrete — not achievable with adaptors
- Method choice drives bit choice, not the other way round
Method 1 — Dedicated Core Drill Machine with Diamond Core Bit
A dedicated core drill machine with a ½" BSP threaded chuck is the professional standard for UK trade core drilling. It runs in rotation-only mode with controlled low RPM and, on machines with integrated water supply, supports wet diamond core drilling for concrete and reinforced concrete.
Suitable for: All diameters from 38mm to 300mm+. All masonry materials including brick, block, concrete, reinforced concrete (wet), and stone. All commercial and domestic applications.
Advantages:
- Consistent low RPM matched to bit diameter — machines have multiple speed ranges
- Integrated water supply for wet coring — not achievable with adaptors
- Higher torque with torque-limiting clutch — handles binding on rebar or dense material without injury risk
- Machine stands and rigs available for large-diameter or floor/overhead coring
- Compatible with the full range of diamond core bits including rebar-rated wet bits
Limitations: Higher equipment cost (£150–£600 to buy; £20–£40/day to hire). Heavier than an SDS drill for small domestic jobs.
This is the correct method for: boiler flues (107mm), extractor fans (107mm), waste pipes (117mm), structural concrete, any hole above 52mm, and any job requiring wet coring. See: core drill machines UK.
Method 2 — SDS Adaptor with Diamond Core Bit (Rotation-Only)
An SDS Plus or SDS Max adaptor fitted to an existing rotary hammer drill allows a diamond core bit to be used without a dedicated core drill machine. The drill must be switched to rotation-only mode — hammer function must be disabled throughout. This method has specific and hard limits:
Suitable for: Holes up to 52mm in standard brick, blockwork, and soft masonry. Cable entries (38mm), small waste pipe penetrations (52mm), and occasional low-volume domestic use.
Advantages:
- No additional machine required — uses an existing SDS drill
- SDS Plus adaptor costs £10–£15; SDS Max adaptor £20–£40
- Compact and light for restricted-access locations
Hard limits:
- Maximum reliable diameter: 52mm with SDS Plus; 65mm with SDS Max in soft masonry only
- No water connection — wet coring is not possible with an SDS adaptor
- Torque management: above 52mm, the torque demand on rebar contact or binding exceeds what the adaptor interface transmits safely
- Machine may overheat on prolonged concrete drilling — SDS motors are not designed for sustained low-RPM rotation under load
- Not suitable for concrete or hard masonry above 38mm
See: SDS Plus vs SDS Max for core drilling for the full adaptor comparison and size limits.
Method 3 — SDS Rotary Hammer with TCT Core Bit
Tungsten carbide-tipped (TCT) core bits are used with an SDS drill in hammer-drill mode — the same mode used for masonry bit drilling. This is the most accessible option for occasional DIY use in standard domestic masonry.
Suitable for: Standard brick, block, and aerated concrete. Small to medium diameters (38mm–100mm). Occasional domestic use — a single hole per job.
Advantages:
- TCT bits cost £5–£25 and fit a standard SDS drill with no adaptor
- Uses hammer-drill mode — no need to switch to rotation-only
- Accessible for DIYers who already own an SDS drill
Limitations:
- Not suitable for concrete, engineering brick, or any hard masonry — TCT bits wear rapidly and produce blowout
- Hammer mode causes spalling around the hole entry and exit — unsuitable for finished surfaces or tiles
- Cannot be used wet — no water supply path
- High vibration in hammer mode — HAVS risk for prolonged use
- Above 100mm: TCT bits become significantly less effective and diamond core bits are required
See: TCT vs diamond core drill bits for the full material-by-material comparison.
Method Comparison
| Method | Max Diameter | Concrete | Wet Coring | Best For |
|---|---|---|---|---|
| Dedicated machine + diamond bit | 300mm+ | Yes | Yes | All trade applications |
| SDS adaptor + diamond bit | 52mm (SDS+) / 65mm (Max) | No | No | Cable entries, 40mm waste pipe |
| SDS hammer + TCT bit | 100mm | No | No | Occasional domestic brick/block |
Which Core Drilling Method Should You Use?
The correct method depends on hole size, material, and frequency of use. For the most common UK domestic and commercial trade applications:
- Boiler flue (107mm through external wall) — dedicated core drill machine with 107mm dry diamond core bit. SDS adaptor not suitable at this diameter.
- Extractor fan (107mm or 133mm) — dedicated core drill machine. Dry bit for brick or block external walls. See: extractor fan core drill size guide.
- Waste pipe (117mm soil stack) — dedicated core drill machine with 117mm dry or wet bit depending on wall material.
- Cable entry (38mm) — SDS adaptor with 38mm diamond core bit on rotation-only is appropriate. Dedicated machine equally suitable.
- Reinforced concrete — dedicated core drill machine with rebar-rated wet diamond core bit only. No adaptor method is viable. See: drilling through rebar guide.
- Tiles (any diameter) — dedicated core drill machine with a tile-rated diamond core bit. No hammer mode. Slow RPM, water cooling or wet sponge. See: core drilling through tiles.
- High volume (10+ holes per week) — dedicated machine ownership is cost-effective. See: hire vs buy a core drill.
Core Drilling Methods: Common Questions
Can I core drill with an SDS hammer drill?
Yes, with important limits. An SDS drill can be used in two ways: with a diamond core bit and SDS adaptor on rotation-only mode (up to 52mm in soft masonry), or with a TCT core bit in hammer-drill mode for occasional domestic use in standard brick and block. For any hole above 52mm, any concrete, or any application requiring water cooling, a dedicated core drill machine is required. SDS drills lack the sustained low-RPM torque, torque-limiting clutch, and water connection that diamond coring above these limits demands.
Which core drilling method is best for a boiler flue hole?
A dedicated core drill machine with a 107mm dry diamond core bit is the correct method. A boiler flue penetration through a standard UK cavity brick wall requires a 107mm diameter hole — above the reliable limit for SDS adaptors (52mm). The dedicated machine provides the correct low RPM (300–500 RPM at 107mm), a torque-limiting clutch for safety, and compatibility with the full range of dry diamond core bits for brick and blockwork.
What is the cheapest way to drill a 38mm cable entry through brick?
A 38mm SDS Plus diamond core bit (£8–£15) used with an SDS adaptor (£10–£15) on an existing rotary hammer drill in rotation-only mode is the most cost-effective approach for a small cable entry. Ensure the hammer function is disabled before starting — diamond core bits are destroyed by percussion. For a single hole, this approach costs under £30 in equipment if you already own an SDS drill.