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Diamond core drilling accuracy — and safety — depends on the supporting accessories as much as the bit itself. A quality core bit run without a pilot drill will walk across the wall face before biting. An undersized SDS adaptor on a large core risks a violent kickback if the bit binds. And on any commercial site, drilling masonry without a Class M vacuum connected to a dust shroud is an HSE compliance issue under CDM regulations.

This guide covers the four main accessory categories: SDS adaptors, pilot drills (guide pins), extension rods, and dust extraction systems.

SDS Max and SDS Plus Core Drill Adaptors

SDS adaptors convert standard SDS Plus or SDS Max rotary hammer drills to accept ½" BSP diamond core bits. They allow plumbers and electricians without a dedicated core drill machine to drill smaller holes through brick and block using tools they already own.

The adaptor must be used on rotation-only mode — never with hammer action engaged. The hammer impacts will fracture the diamond segments almost immediately.

  • SDS Plus adaptor: Suits core bits up to 52mm in soft masonry. Limited by the SDS Plus shank's torque capacity. Standard rotary hammers with SDS Plus (typically 700–1100W) handle 38mm and 52mm dry cores in brick without issue.
  • SDS Max adaptor: Suits core bits up to 65mm, occasionally 82mm in soft brick with a powerful 1300W+ hammer. The larger shank handles higher torque. Recommended for the 52mm and 65mm sizes that fall in the borderline zone between adaptor and dedicated machine use.

For a full comparison of SDS Plus vs SDS Max adaptors including which specific machines they suit, see the SDS Plus vs SDS Max guide.

Pilot Drills (Guide Pins)

A pilot drill — sometimes called a guide pin — is a standard twist or masonry drill that fits through the centre of the core barrel and locates in a pre-drilled pilot hole. It centres the core bit on the entry point and prevents the hollow barrel from skating across the surface before the diamond segments engage.

Most diamond core bit kits include a 200mm pilot drill. For deep drilling with extension rods, a longer pilot is required to maintain centring through the full depth. Pilot drills are consumables — replace them when the tip wears, as a worn pilot allows the core barrel to drift and produces an oval rather than round hole.

Extension Rods

Standard diamond core bits cut to 150mm effective depth. For walls thicker than 150mm — solid brick, double-skin masonry, insulated cavity walls, or structural concrete — extension rods thread between the core bit and the machine chuck to increase cutting reach.

Extension rods come in 300mm and 500mm lengths. Multiple rods can be threaded together for very deep cores. Key points:

  • Always match the thread type to your core bit (½" BSP is UK standard).
  • Verify the rod's torque rating against your machine output — under-rated extensions can fail under load.
  • A longer extension introduces flex. For precision work, add a guide rod bracket or use a drill stand to maintain alignment.

Dust Extraction and Dust Shrouds

Drilling through concrete and masonry produces respirable silica dust — a Category 1 human carcinogen under IARC classification. In the UK, the COSHH regulations require adequate dust control on any notifiable construction activity involving silica-generating materials.

A dust shroud fits over the core bit and wall face to capture arisings at source, connected via 35mm hose to a Class M or Class H vacuum. For wet diamond coring, the water also suppresses airborne dust, making a shroud less critical — but a vacuum still assists with slurry management.

For dry coring indoors — boiler flues through internal brick partitions, cable entries through concrete floors — a dust shroud connected to at minimum a Class M vacuum is both a legal requirement on commercial sites and a practical necessity to avoid contaminating the interior.

See the core drill machine guide for machines with integrated dust/water shroud connection points.

Core Drill Bit Sets

For UK tradespeople who cover multiple applications, a multi-bit kit with a common ½" BSP adaptor and pilot drill is more economical than buying individual bits. The Marcrist PC850 and CCU850X kits (38mm, 52mm, 117mm) cover the three most common UK trade sizes — cable entry, basin waste, and 110mm soil pipe — in a single purchase. The Erbauer 5-piece set adds 65mm and 127mm for a broader range at a lower price point.