Core Drilling

Learn all about core drilling, why it’s performed, the types of core drilling, the risks involved, and safety measures to take to reduce the risk.

construction worker drilling a construction site with a core drill

What is Core Drilling?

Core drilling refers to the process of using a hollow drill to bore holes through certain surfaces. Through core drilling, teams can learn the density, chemical composition, strength, and other properties of specific materials.

The reason it’s important to use a hollow drill is that the purpose of core drilling is to extract a sample from the surface. The extracted sample is then brought to a lab for further testing. This is commonly used in mining and concrete work. However, it’s also used in other industries where teams need to get data on certain materials.

Core drills penetrate various surfaces. So, the process can be used to gather stone, wood, and even ice samples.

Why Use This Method?

Core drilling is an important process for any project that requires gauging the properties of different materials. In some cases, teams may prefer using techniques such as mud rotary drilling. The downside to this, however, is that it doesn’t get as accurate as a sample as core drilling, as the mud rotary drilling process can leave up to 3 inches of subsurface data.

Using a core drill bit does take some more work and requires more effort. However, it also allows teams to gather a more accurate sample that will provide them with very valuable information down the line.

How Does It Work?

The basic concept of core drilling is using a hollow bit to extract a sample from a certain surface. There are two types of core drilling, and each of these processes works in a slightly different way.

Soft Coring

Soft coring is used for unconsolidated material. The process is effective up to depths of 500 feet. However, the equipment for soft coring can reach deeper depths, provided the right conditions are met.

This process uses nested barrels. It has an inner barrel that pushes out and captures the samples, while the outer barrel protects the hole from collapse, serving as a sort of case. This also ensures that there’s no contamination from air or fluids when the sample is extracted.

Hard Coring

Hard coring is used for extracting competent rock samples. While this process also uses nested barrels, it’s the outer barrel that extends in this process. This washes the surface with drilling fluid or air before the drilling takes place. That way, the sample remains undisturbed.

This process can reach depths of up to 5,000 feet and is also called diamond coring due to the diamond-coated drill bit needed to penetrate the rock. This is widely used for samples that are harder than sandstone.

What are the Risks of Core Drilling?

The risks workers face when core drilling can vary depending on the type of material being extracted, the location, the equipment used, and more.

For example, one of the major risks associated with core drilling is the particles that may enter your lungs during the process. When drilling concrete, there is a fair amount of silica dust released into the air, which can cause significant damage when inhaled.

Additionally, the process of drilling into hard substrates is also very loud. It’s important to monitor the noise levels when core drilling and ensure that employees aren’t exposed to loud sounds for too long. If exposed to loud noises for a long period, employees are at risk of developing hearing problems and other complications.

Another consideration is physical fatigue. Drilling into hard rock and other materials can take a lot of time and effort. This can drain workers, so it’s important to consider how much the employees are working and avoid overloading their schedules.

Best Safety Practices For Core Drilling Operations

There are some risks to core drilling that organizations will have to accept, especially when weighed against the benefits of core drilling. This is why it’s important to have a solid set of safety practices to alleviate the risks associated with core drilling.
Some of the best safety practices to keep in mind when core drilling include:

  • Always wear appropriate Personal Protective Equipment (PPE) while at work (e.g., eye mask, dust mask, gloves, etc.).
  • Do not use tools that have suspected damage or defects.
  • Only use barrels that are suitable for your drill and the materials you’re drilling.
  • Inspect equipment thoroughly before use.
  • Service and maintain drilling equipment properly.
  • Train employees in the proper use of different drilling equipment.
  • Keep a fire extinguisher nearby.
  • Ensure that the driller and shaft have a tight and secure fit.

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Core Drilling Machines

There are different types of core drilling equipment to be used depending on the specific application. Here are some of the most common types of core drilling machines:

  • Universal core drilling machine – This is ideal for drilling projects where it is necessary to core at any angle.
  • Portable core drilling machine – This machine is composed of three main parts: an electric motor speed reducer, support column, and light alloy base. One of its main features is that it can be assembled and disassembled, making it easy to transport.  
  • Laboratory coring machine – This equipment is specially designed for laboratory use—cutting hard materials such as rocks and concrete for example.
  • Pavement core drilling machine – This heavy-weight machine can be used for all types of material, yet is portable enough to be transported to different fields. 

FAQs about Core Drilling

Core drilling is necessary when you need to assess the properties of a certain material. It is also the safest and fastest way to drill through concrete.

This depends on the process and the material you’re drilling. Generally, core drilling depths can reach between 500 to 5,000 feet while the diameter ranges between 3/4 of an inch to six feet.

Yes, you can use dry core bits to core drill without water. When dry core drilling, it’s important to take all the appropriate safety measures to protect yourself from its hazards. For example, breathing in fine dust can be prevented by wearing a Powered Air Purifying Respirator (PAPR) and installing a dust extraction system.

Anchoring the rigs is essential to drilling a straight core. To do this, it’s best to use physical anchors that are designed for core drilling.

Leon Altomonte
Article by

Leon Altomonte

SafetyCulture Content Contributor
Leon Altomonte is a content contributor for SafetyCulture. With his language degree and years of experience in content writing, he delivers well-researched, informative articles about safety, quality, and operational excellence. In addition to his professional pursuits, Leon maintains a creative outlet as a performing musician.