Bits ‘n Pieces – The Driller’s Blog

Fundamental Guide to Choosing the Right Core Bit Configuration

Posted by Rod McCoremick on Dec 12, 2016 10:30:00 AM


The question we hear most often from customers is “how do I choose the right core bit for the ground I will be drilling in?” So last year we wrote a guide on that and it was very popular. Many variables need to be considered including rock hardness, the variability of the rock, and whether it was abrasive, and then you need to choose the right bit range and configuration. While we have scratch tests to help determine bit range, how do you choose the configuration?


 
That has always been a bit of a mystery, so we decided that we should help demystify how you go about choosing the right core bit configuration. In general, you want to choose a configuration that will help ensure drilling fluids reach the bit so that they cool the bit and effectively flush drill cuttings. This will help extend core bit life. There are many choices available when it comes to configurations, but they involve two main types of options.

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Waterways

When choosing your configuration, you need to consider the waterways through which the drilling fluids will flow. You will need to choose the shape of the waterways, the number of waterways and the width of the individual waterways. For example, pie-shaped waterways tend to flush rock cuttings away more easily in soft and broken rock.

In general, when drilling in softer, unconsolidated ground you should consider wider waterways and when drilling in harder competent ground, you should consider narrower waterways. To obtain more cutting ability from the bit with less weight on the bit (WOB), you should consider adding more waterways to your configuration.

 

Discharge options

A basic configuration will usually be sufficient for ejecting drilling fluids in typical, competent ground. However, a discharge option can be useful in creating additional space for the ejection of cuttings in block-like formations. Discharge options include deep waterways, lateral discharge, face discharge and more.

 

Other options

It is important to note that other options or add-ons are available that can help tailor your core bit configuration to meet your drilling requirements. Often, when drilling in abrasive ground conditions, the loss of the inner or outer gauge of the core bit can become an issue. You may choose to investigate reinforcing the inner or outer diameters to ensure optimal core bit lifespan.

 

When performing deep hole drilling, you may want to consider different crown height configurations to extend core bit life. In some cases challenging drilling projects may require special adjustments to the core bit. In these cases, a discussion with a technical representative would be recommended.

 



CONCLUSION:

The large number of configuration choices can be overwhelming, making it hard to know which one to pick. While you may have had success with one type of configuration and stuck with it over time, you may find yourself in a very challenging ground condition where that configuration no longer performs well. You then have to investigate an array of configuration options that you may not be familiar with. To help you make an informed choice, we consulted our technical experts, gathered their recommendations, tips and advice and put it all together into a new resource for you: the Fundamental Guide to Core Bit Configurations. It provides even more detail about discharge options, choosing waterways and more.  Consider it our new gift to you because our mission is to help you improve your drilling performance.


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Topics: How to choose equipment

Fordia works with its customers in mineral exploration and the geotechnical and environmental drilling industries, to provide high-quality drilling solutions that increase productivity, lower costs and make life easier for the drilling community.