Diamond Core Drill Bits

A diamond core drill bit (core bit) is a tubular tool with diamond segments on its face that cuts a cylindrical hole and leaves a core behind. It makes clean holes in concrete, reinforced concrete, stone and masonry for services: plumbing pipes Ø 52–110 mm, ventilation Ø 100–200 mm or electrical boxes Ø 68 mm. Diameters range from about Ø 8 mm to over Ø 350 mm. Unlike a percussion bit, the core bit does not hammer the material apart but grinds it, giving a smooth hole without cracking.

The bit is mounted on the core drill spindle via a 1 1/4″ or R 1/2″ thread, and the machine is stabilized on an anchored or vacuum base plate. Drilling starts at lower speed, then you keep a steady feed pressure and cooling: wet with water at about 2–4 l/min, dry with an M-class vacuum. Speed drops as diameter grows — from a few thousand rpm at Ø 50 mm to a few hundred at Ø 200 mm.

Wet drilling cools the bit with water (about 2–4 l/min), which lowers segment temperature, flushes out the slurry and extends tool life — it is the method for reinforced concrete, hard concrete and large diameters up to Ø 350 mm, done with a core drill fed by water. Dry drilling removes dust with an M-class vacuum and is used for concrete, brick and masonry, usually up to Ø 150 mm, with a handheld drill. For reinforced concrete, wet drilling is recommended.

For reinforced concrete you choose a laser-welded segmented bit designed for wet drilling and for cutting through rebar. The hard segment bond withstands contact with steel, and water cooling at about 2–4 l/min protects it from overheating. The work is done with a rig-mounted core drill, not a handheld one. For diameters over Ø 100 mm it is worth using a 100–300 mm extension. Bits of this kind come primarily from Tyrolit — electroplated bits are not suitable for reinforced concrete.

The price of a diamond core bit depends mainly on diameter and segment class. Small Ø 25–50 mm bits for dry drilling usually cost from about PLN 150–400, popular service diameters Ø 68–132 mm roughly PLN 400–1,200, and large Ø 200–350 mm bits for wet reinforced-concrete drilling from several hundred to several thousand zloty. Accessories add to the cost: 100/200/300 mm extensions and a thread adapter. Current prices of Tyrolit models are given on the product pages.

A diamond bit has segments of diamond powder sintered with metal on its face and grinds the material, so it handles concrete, reinforced concrete, granite and hard stone. A carbide bit (TCT, tungsten carbide) cuts with tungsten-carbide edges and works in softer materials: brick, aerated concrete, hollow blocks and masonry — it is cheaper, but blunts quickly in reinforced concrete and will not cut steel. For Ø 100–200 mm holes in reinforced concrete, diamond core bits are used.

The bit diameter is matched to core-drill power and hole type. Handheld diamond drills usually take bits up to Ø 100–130 mm, rig-mounted core drills up to Ø 200–250 mm, and the most powerful units above Ø 350 mm. The bit thread (1 1/4″ or R 1/2″) must fit the spindle — if it differs, an adapter is used.

An extension rod for core drill bits is a part fitted between the core-drill spindle and the bit that increases drilling depth. It comes in 100, 200 and 300 mm lengths, with a 1 1/4″ or R 1/2″ thread matched to the bit and machine. Extensions are used when the wall or slab is thicker than the usable length of the bit — for example when drilling through a 40–60 cm wall. They can be chained in series up to the required depth.

Tyrolit bits and extensions come in two thread standards: 1 1/4″ UNC and R 1/2″. The 1 1/4″ (imperial, UNC) thread is the standard for large bits Ø 82 mm and up on rig-mounted core drills. The R 1/2″ (BSP) thread is used on smaller bits and adapters for handheld drills. The thread is matched to the machine spindle — if it differs, you need a 1 1/4″ to R 1/2″ adapter, available together with the Tyrolit 100/200/300 mm extensions.

A single universal bit will manage concrete, natural stone and granite, but at the cost of durability and speed — segments and bond are optimized for a specific hardness. Bits for reinforced concrete have hard segments resistant to steel, while porcelain stoneware and tiles need thin electroplated bits Ø 6–68 mm. A company doing varied holes is better off with 2–3 dedicated bits rather than one universal one — for concrete and reinforced concrete we recommend laser-welded segmented Tyrolit bits for wet drilling.