How Is Core Drilling of Concrete Done

Contents

– When and how to core drill concrete?

– What are the precautions to be taken for concrete coring and the maintenance of coring tools?

– What is the price of concrete core drilling?

While it is always a question of penetrating a wall, there is a difference between drilling and coring concrete depending on the diameter of the opening to be made. While drilling a small diameter hole can be done with a drill and bit or a concrete drill bit, core drilling requires a powerful machine (drill, drill press or core drill with a diamond bit).

When and how to core drill concrete?

Purpose of concrete coring

A core drill is used to make a circular opening in a material with a large diameter. This core drilling can be vertical or horizontal, depending on the substrate in which the hole is to be drilled.

Concrete coring is mainly used in the building and public works sector to:

 – cleanly open (unlike what a jackhammer or chisel would do) passages for ducts, conduits, pipes and channels through walls (air conditioning, heating, climatic appliances, etc.) 

– incorporate metal structural elements into an existing construction (renovation, building extension, etc.), 

– take over or redo the construction of a new building, etc. …),

– take over or rebuild pipes buried under the road, and take samples of asphalt and bitumen (search for asbestos in asphalt).

Concrete coring method

It is necessary to use a more powerful machine than a simple drill (note that core drilling does not require percussion) and specific drill bits to carry out a core drilling operation.

With a core drill

A core drill is an electro-portable machine with a rotating chuck, which is usually electric (although there are some petrol-driven core drills), mainly used for soil sampling.

Compared to a drill, the core drill is equally powerful. Usually, it has a water circulation system to feed water into the drill bit to wash the wall of drilling dust, facilitate the penetration of the diamond tool, and cool it during drilling if the diamonds in the bit require it.

Caution: A core drilling machine must be fully protected against electrical hazards, especially when the device is to be used with water. As a rule, the machine has an integrated earth leakage circuit breaker and waterproof switches.

With a crown

The drill bit resembles a significant hollow drill bit, or a hole saw of the appropriate diameter for core drilling. The drill bit’s cutting edges are fitted with synthetic diamonds that are harder than the materials to be drilled through, including concrete and even concrete reinforced with rebar.

There are diamond core bits, which are used dry, and others that are used with water circulation. A water drop symbol indicates that it is used exclusively with water, while the crossed-out drop means that the bit is used dry.

Good to know: Hole saws with a large diameter (up to about 40 mm) but not very deep are usually called “drill bits”, whereas core drills use large diameter (up to more than 300 mm) and long drill bits to cut through thick walls.

Use of a drill stand

If a heavy core drill is used and a perfectly straight core drill is required (horizontal or vertical), it quickly becomes necessary to use a stand on which the core drill is fixed during the whole work.

There are vertical core drill stands placed on the ground and horizontal ones fixed to the wall to be drilled through; some core drill stands can be used vertically and horizontally.

Good to know: rarer and mainly used by professionals, the vacuum core drill supports (with a vacuum pump) allow the core drill to be placed on a support that does not support pegging (with prior drilling), which is particularly suitable for walls covered with cladding or wall coverings that need to be preserved.

What precautions should be taken when drilling concrete and maintaining core drilling tools?

Preliminary precautions

Before drilling a core borehole, it is important to ensure that the inside of the wall you wish to drill through is free of any circuits or pipes.

Depending on the diameter of the hole to be drilled and the thickness of the wall or the depth of the borehole, a drill bit of the appropriate diameter and length is chosen.

The choice of the diamond core bit may then require a wet core drilling rather than a dry one; it is then necessary to consider the necessary use of water (presence of an electrical risk) and the muddy water contamination that the core drilling will produce.

Good to know: experienced professionals generally do not need a core drill stand when the core diameter is less than 80 mm, and a light core drill is used (about 2000 W).

Water supply

It is then usually necessary to fix the core drill stand to the wall or floor before mounting the core drill with the drill bit on the drill stand.

When water is required for drilling, it can be supplied by a hose. Still, it is also possible to use a canister to provide a water supply, taking care to keep the water supply above the level of the core drill (gravity supply) or a pressurised canister.

Mounting the crown

The assembly of the drill bit on the core drilling machine is done by making sure that it is well centred and sometimes by interposing a specific ring to prevent the blocking occasionally inherent in the torque during the drilling.

The core drilling is then carried out by activating the machine after setting the desired rotation speed defined by the diameter of the drill bit and by ensuring that water circulation is possible when necessary.

Good to know: it is essential before using the core drill (and even more so when used with water) to ensure that the integrated differential circuit breaker is working correctly. The circuit breaker is usually equipped with a test button for this purpose.

Cleaning the crown

Once the core drilling has been completed, the drill bit is cleaned with water, checking the condition of the diamonds for future use.

The core drill is cleaned with a compressed air jet, paying particular attention to the motor cooling vents.

It is recommended to grease the shaft on which the crown is mounted, but never the crown itself.

Note: a professional may need to buy a core drilling machine, but a private individual will rarely make the purchase (about $1,500 to $2,500) or the maintenance (engine, gearbox, clutch, shaft, bearings, etc.) profitable.

What is the price of a concrete core drill?

There are two ways to get a concrete or asphalt core drill: do it yourself or have it done by a professional.

Core drilling by private individuals

It is possible to hire a core drill, often with a stand to attach it to.

The rental price is a little over $100 per day from a professional rental company, but it is sometimes possible to get a half-day rate.

The crown is usually purchased in addition to the rental, as it is a consumable accessory.

Good to know: it is often better to buy the crown in a tool shop or on the internet rather than from the professional hirer, who sometimes sells them at a higher price and offers much less choice.

Drilling by a professional

When a professional has to drill a core hole to install an appliance or run a pipe, he will charge you depending on the thickness of the wall and the diameter of the core hole.

Good to know: when renting a core drill from a private individual or a professional rental company, it is a good idea to include a suction cup support with a vacuum pump for work on cladding, siding or plaster, as well as a water and dust hoover, to avoid the dispersion of muddy water in the premises.