Concrete core drilling (also known as concrete coring) is the mechanical process of drilling a precise circular hole in concrete structures such as walls and floors. It involves the use of a core bit attached to the end of a core drill to perform the cutting. Diamond tipped segments placed at the end of a core bit perform the cutting as the core bit spins or rotates whilst making contact with the surface to be cut.
Core drilling is suitable for drilling holes through concrete, masonry, asphalt, stone, or other solid surfaces. Core holes are able to be drilled horizontally, vertically inverted, or angled.
The core bit removes approximately 4mm of the material which is cut by the segments of the core bit during the drilling process. The inner section that becomes free is known as a core, hence the reason drilling of this nature is known as "core drilling".
Drilling a hole on a precise angle is best achieved by utilising a dedicated drill mounted on a drill stand. In order to drill a hole on a specific angle, the drill stand post is adjusted to the appropriate angle to suite.
Care needs to be taken when starting the hole as the core bit doesn’t strike the surface perpendicular, rather the segments of the core bit engage one at a time. Do not apply to much pressure at this stage of the drilling process as this is likely to lead to misalignment, jamming, or segment loss.
There really isn’t a limit or fixed depth a hole can be drilled. Technology exists to drill as deep as needed. Using continuous tubing you can just add as many sections of tubing needed to complete the core as long as there is enough power to rotate the drill and water pressure to keep the drill bit or core barrel cool and flushed of debris.
Core bits can be manufactured approximately 1.2 metres in diameter or 120 centimetres. Whilst we ourselves do not have one that large as we haven’t had a client request for this size to date, we have several large size core bits with the largest being 0.9 metres in diameter.
In addition to this, if the hole size needs to be larger and still circular, this can be achieved by stitch drilling the penetration.
Put simply, it represents drilling through a ceiling surface thereby drilling upside down as access from above is either restricted or the holes required only need to be on the underside of the concrete and partially drilled thereby not penetrating through to top side of the surface.
Due to the use of water during the drilling process, the standard electric drilling equipment isn’t suitable. Rather hydraulic or IP rated (waterproof) electric drilling equipment must be used. In addition, a slurry ring is placed around the core bit to capture the waste water generated by the drilling process.
Best suited where a larger style penetration is required in a wall where overcutting the corners is not permitted. Stitch drilling represents the process of linking single core holes together to form a linear line. The holes are drilled such that they overlap slightly in order to achieve a consistent line in the direction and length required for the penetration.
Due to the close proximity of holes needing to be drilled when stich drilling, it is a perfect application for the use of auto-feed drilling rigs, an automation technique where a single core driller can operate multiple drilling rigs at the same time leading to significant advantages including the speed in which the drilling can be completed.
As core drilling is non-percussive it results in minimal vibration and uncontrolled movement. By reducing the amount of vibration, the diamond drill reduces the amount of uncontrolled or sporadic movement when initially penetrating the surface. This results in greater control over the diamond core drill and in turn the precise location of the core bit penetration point.
The combination of water suppression fitted to core drills and the hollow centre of the diamond core bit have been designed specifically to allow water to act as a coolant as well as a dust suppressant as it passes from the drill through the core bit to the point of contact being drilled. It is for this reason core drilling is sometimes referred to as wet drilling.
The importance of this feature, i.e. the dust suppression, cannot be stressed enough. Crystalline Silica represents a harmful particle substance contained in concrete, sandstone, and other solid surfaces. Inhalation of crystalline silica has the potential to cause various illnesses including asthma, chronic obstructive pulmonary disease and most significantly crystalline silicosis where exposure is significant in nature or prolonged.
The use of water as a suppressant results in the dust generated being kept wet throughout the drilling process thereby preventing the dust particles from becoming airborne. The slurry, or waste generated is then collected using a vacuum called a Wet Vacuum.