Dry vs Wet Core Drilling: Which Method for Which Material?
Drill dry in brick, block and most unreinforced concrete, with dust extraction. Drill wet in heavily reinforced concrete, granite, natural stone and vitrified porcelain, where water cools the diamond segments and flushes slurry out of the hole. The material and the reinforcement decide the method, not the machine you happen to own.
The method then decides the bit, and whether you drill hand-held or on a rig. Dry and wet cores are not interchangeable, and the WCU wet cores are rig models that need a stand, so check the stated application before you buy. Compare them on our diamond core drill bits page.
Should you core drill dry or wet?
Work down the material column to the job in front of you. Where a bit is named, that is the range sold for that method. The method column tells you whether the bit is run hand-held or rig-mounted on a stand.
| Material | Reinforcement | Location | Method | Dry or wet | What you need |
|---|---|---|---|---|---|
| Brick, block, blockwork | None | Indoors | Hand-held | Dry | Dry core bit, dust extraction, pilot drill |
| Facing brick, engineering brick | None | Outdoors | Hand-held | Dry | DCU550 or DCU750X, pilot drill |
| Hard brick: Class A engineering brick, such as Accrington Nori | None | Indoors or outdoors | Hand-held | Dry | PC850 or CCU850X, dust extraction |
| Unreinforced concrete | None or light | Indoors or outdoors | Hand-held | Dry | DCU750X, CCU850X or PC850, dust extraction |
| Reinforced concrete | Rebar present | Outdoors, plant room, riser | Rig-mounted or hand-held | Wet | WCU750X or WCU850X on a stand, water feed; or CCW850X hand-held |
| Heavily reinforced or flint concrete | Heavy | Indoors or outdoors | Rig-mounted only | Wet | WF850X, stand, water collection |
| Natural stone, granite | n/a | Indoors or outdoors | Rig-mounted or hand-held | Wet | WCU550 or WCU750X on a stand, water feed; or CCW850X hand-held |
| Vitrified porcelain, outdoor ceramics | n/a | Indoors or outdoors | Hand-held | Wet (required) | PG850V, water feed |
| Anchor holes 12-40mm | Heavy | Indoors or outdoors | Rig-mounted or hand-held | Wet | WCU850X-F, water feed |
Three bits are sold as combination cores, and each has its own job:
- The CCU850X is the Combi Core Universal. It drills hard materials dry and hand-held, including reinforced concrete, granite and Class A engineering brick, and it can also be run wet. It has a 1/2" BSP (F) thread.
- The PC850 is the Percussion Core. It drills dry from a percussion or rotary drill with the percussion left on, but not in SDS hammer mode. It has a 1/2" BSP thread.
- The CCW850X is the Combi Core Wet, for hand-held wet drilling with minimal water in reinforced concrete and natural stone. It has a 1 1/4" UNC thread.
What lets the combination cores cut harder material than a standard core is the segment: a softer bond and larger diamonds, which keep the segment cutting in hard material instead of glazing over.
How does dry core drilling work?
A dry core bit cuts without water. Air through the barrel and past the segments carries the heat away, and the dust is pulled out by an extractor rather than washed out. Marcrist's own description of the range is direct: dry core bits cut without water and suit hand-held drilling.
The DCU range, short for Dry Core Universal, is the dry family. The DCU350 is a slotted trade core for brick, block and soft to medium masonry, 38-127mm. The DCU550 covers brick and block up to Class B engineering brick, 38-152mm. The DCU750X is the universal dry core, 22-200mm, and the store states it drills clean holes without water or cooling agents. For harder Class A engineering brick, step up to the CCU850X or PC850.
Dry drilling is quicker to set up and leaves nothing to mop. Its limit is reinforcement: once the segments hit rebar with no water to cool them, a standard dry core gets hot and slows down.
How does wet core drilling work?
A wet core bit is fed water through the machine or a swivel. The water does two jobs: it cools the diamond segments, and it flushes cuttings out of the kerf as slurry, so the bit keeps cutting fresh material instead of grinding its own debris.
The WCU range, short for Wet Core Universal, is the wet family, and every WCU core is a rig model: run it on a stand. The WCU350 covers blockwork, brick and concrete, 42-250mm. The WCU550 suits natural stone and soft to medium concrete, 42-225mm. The WCU750X and WCU850X both run to 350mm for reinforced concrete and natural stone, and the WF850X is sold for rig-mounted drilling in extremely hard reinforced and flint concrete.
For hand-held wet drilling, use the CCW850X combi core instead.
How do you manage dust and water when drilling indoors?
Indoors, dry drilling is normally the right call in brick, block and most concrete, with dust extraction connected from the start. Silica dust is the reason. The Marcrist DDM1 and DDM150 are dry core drills built to work with dust extraction.
If the material forces you wet indoors, the water has to be caught, not chased. A water collection system collects slurry at the face and mounts to the DS300 and DS355 rigs.
Treat electrics as a separate discipline. On a 240V machine, use an RCD; keep connections out of standing water, and follow the machine's instructions. The DDM200 and DDM300 are both stated to carry an inline PRCD on the 240V version.
Why is wet drilling usually the answer in reinforced concrete?
Because rebar is steel, and steel does not cut like aggregate. A segment meeting rebar heats up fast, and with no water there is nothing to take that heat away. The store's guidance is to drill wet in heavily reinforced concrete and very hard materials, where the water cools the segments and flushes out the slurry.
The range says the same thing. The DCU550 FAQ states it is designed for non-reinforced materials and recommends a wet core bit for reinforced jobs. The DCU350 is dry only too: for wet drilling, use the CCW850X or the WCU series. Hitting rebar regularly is a signal to change method, not to push harder.
WCU wet cores want a stand. The WCU350, WCU550, WCU750X and WCU850X are all rig models. Our core drill stands and rigs include the DS180 for cores up to 180mm and the tiltable DS355 Titan for cores up to 355mm. Mount with a vacuum plug set on sound concrete; on brick you need anchor bolts, because brick will not hold vacuum.
Which threads and machines suit each method?
Most hand-held dry core bits use a 1/2" BSP (F) thread and most wet core bits use 1 1/4" UNC. It is why an adaptor is so often the missing piece. Check the fitting stated on the product page, because it is not uniform across the range.
On machines, the DDM150 is stated to be for dry core drilling only. The DDM200 is stated to suit either dry or wet core drilling, hand-held or rig-mounted, with a 1/2" BSP(F) and 1 1/4" UNC(M) spindle. The DDM300 is a wet machine with an inbuilt water connection, pictured below with its water tail, valve and push-fit hose connector fitted. Compare them on the diamond core drills page.
For BSP to UNC, SDS Plus, 3-jaw chuck, M14 and Hilti conversions, see our core drill adaptors and the full core drill adaptor and thread guide. The most common one, a 1/2" BSP (M) to 1 1/4" UNC (M) adaptor, is shown below.
What do you need for each method?
Dry kit list: a dry core bit from the DCU range, or the CCU850X or PC850 for hard brick and concrete; a dust extractor connected at the drill; a pilot drill through the centre of the core so it locates the hole and stops the bit skidding on the surface; and an adaptor if your machine thread does not match the core. Many Marcrist cores also have rooftop segments that make starting easier.
Wet kit list: a wet core bit from the WCU range with a stand, or the CCW850X for hand-held work; a water supply; an RCD if the machine runs on 240V; a machine you have read the instructions for; and, indoors, a water collection system. For hand-held and light rig work a 3 litre water pressure bottle is enough. For longer runs, the 11 litre water pressure container is stated to suit diamond core drills and drilling rigs.
Diameter matters as much as method. Our core drill bit size chart covers UK sizes for soil pipes, fan ducts and flues, and six core drilling problems and how to stop them covers glazing, snatching and rebar.
Frequently asked questions
Can you core drill dry into concrete?
Yes, in unreinforced concrete, with a dry core bit and dust extraction. The DCU750X is sold as a universal dry core for brick, block, concrete and stone, and the CCU850X and PC850 combination cores drill concrete dry as well. Once there is rebar in the slab, switch to wet, or see the CCU850X below.
Do you need water to core drill concrete?
Not for most unreinforced concrete, where a dry core and an extractor will do. You do need it for heavily reinforced concrete, granite and very hard materials, where it cools the segments and flushes the slurry out.
The exception is the CCU850X, the Combi Core Universal. Its softer bond and larger diamonds let it drill reinforced concrete, granite and Class A engineering brick dry and hand-held, with an extractor connected, and it can also be run wet when you prefer to.
Can you use a dry core bit with water?
The DCU range is sold as dry core bits, and the DCU350 product FAQ states it is intended for dry use. For wet drilling, use the CCW850X or the WCU series instead. Check the stated application before changing method.
Can you core drill wet indoors?
Yes, but only with the water controlled. Use a water collection system at the face, keep electrical connections clear of water, and on a 240V machine work through an RCD. Where the material allows, dry drilling with extraction is easier indoors.
Can you run a diamond core bit in an SDS drill?
Yes, with an SDS Plus adaptor and the hammer action switched off, so the drill runs on rotation only. The PC850 is designed to run on percussion drills with percussion on, but not in SDS hammer mode.
Choosing your core bit
Match the bit to the material and the reinforcement first, then decide hand-held or rig, then check the thread and the diameter. Dry for brick, block and most concrete indoors, with the CCU850X or PC850 for hard engineering brick. Wet for reinforced concrete, stone and porcelain: a WCU core on a stand, or the CCW850X hand-held. Browse the full range of Marcrist diamond core drill bits, or start from the machine on our diamond core drills page.