Bits ‘n Pieces – The Driller’s Blog

Which Core Bit to Use When Wedging?                  The Prism60

Posted by Rod McCoremick on Jun 26, 2019 11:27:00 AM

Bore hole deviation is one of those things that occur despite all the preventative measures and precautions that diamond drillers may take. Deviations may occur due to equipment that is lost and stuck in the bore hole or it may be intentional because the geologist has requested a new trajectory. A deflection wedge is one of the oldest and simplest ways to steer the bore hole. There are other choices for directional drilling and you can read about them in this blog.


Wedges are a quick and easy way to drill around tools that have become stuck in the hole, such as drill rods and core barrels. Once the wedge is in the bore hole however, you will need to be careful with all your down hole tooling and in particular the core bit. You have taken a lot of care choosing the right core bit, and you don’t want to damage it before you get as much life out of it as possible.

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When the wedge is positioned in the hole, you can damage the tip of the core bit crown when you try to drill past the wedge, or worse yet, you can drill through the wedge. We have a wedge bit called the Prism60 that is the perfect bit for drilling and coring after you have installed a defection wedge because of its shape. The Prism60 is part of Fordia’s Prism family of products for directional drilling. The Prism line also includes the Prism Directional Wedge as well as other specialized tools.

The Prism60 has a smoother 60 degree angled chamfer on the leading edge of the bit and this makes it easier to drill past the wedge without catching. Its inner and outer diameters have been reinforced with diamonds so that the bit cuts better and the waterways are improved to deliver more water flow to the shoulder of the bit keeping it cooled and intact. With its flat crown, it gives you more matrix for a longer lifespan.

You need to remember that the Prism60 is not the only bit you need to consider. You may have used the wedge bit to drill past the wedge and have progressed nicely down the hole when you realize that your bit is finished and you need to change it. For any second or subsequent trips down the hole past the wedge, you don’t need the 60 degree angle and can use a bit with a 112 degree angle on the chamfer. This slight chamfer allows it to perform better than a squared edge of a regular bit, making it less likely to catch on the tip of the blade of the wedge or on any broken formations. For drillers who don’t like using a graphite plug for going past a wedge, it is a good alternative. What’s more, it’s great for holes with multiple wedges.


Wedging can be a tricky business and this is why manufacturers continue to innovate and find new equipment and tooling that can help drillers improve performance and lower operational costs. Drilling tools like these new bits for wedging are allowing diamond drillers to avoid damaging precious equipment. Our technical support team can help you with advice on the new line of Prism tools for directional drilling.



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Topics: Tips on common drilling issues, Basic drilling information, How to choose equipment



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