Core Bore Bit–5 Tips for Choosing Core Bore Bit

Today we have different surfaces that require using different types of core bore bit to drill. Now, it is no news that using a core bore bit can be complicated due to all the factors you consider before selecting one that will best fit your purpose. As such, this article addresses this concern by bringing into focus the different factors and useful tips you must have in hand before selecting a core bore bit. This article answers and clears your doubts before choosing a core bit.

A Diamond Core Bore Bit
Figure 1: A Diamond Core Bore Bit

1.Core Bore Bit–Surface Hardness

The very first factor most users have to consider in choosing a diamond bit is surface knowledge. Knowing all you need to know about a surface will most definitely start you off on the right foot. Of all of the things to know about the surface, the “Surface Hardness” ranks top. Now you can ask yourself, how do you know your surface hardness? Simple, you either have to use the Mohs Hardness scale or your traditional pocket knife technique.

The Mohs Hardness scale consists of a rating ranging from number 1 through to number 10. They also rank softest to hardest in that order (1 is the softest and 10 is the hardest). On the other hand, if you are not feeling up to all that stress, you can easily use your pocket knife, which usually ranges between 6.0 and 6.5 in the Mohs Scale rating.

Knowing the surface hardness is essential because manufacturers design the different drill matrices to perform specific ranges of the Mohs Scale. Ultimately, understanding the hardness of the surface will help you pick the best bit suitable for the surface. Choosing a suitable drill will help you cut faster and trip lesser. As a rule of thumb, know that surfaces with a higher Mohs scale rating will scratch anything with lower Mohs hardness.

However, some surfaces can prove rather tricky because even after testing the surface hardness, as you begin to drill, this hardness seems to change. If you happen to encounter such, that many know as “Surface Variability,” you must look out for custom made core bore bit that can cut through such surface effectively.

Surface for Drilling
Figure 2: Surface for Drilling

2.Core Bore Bit Grade

After you have an understanding of the surface hardness, the next thing is choosing the core bore bit. Now, different manufacturers provide a bit hardness rating and comparison chart to help the consumer have a good understanding of the ability of the core bore bit.

These charts are often colour-coded for easy classification. You can divide these classifications based on the Mohs Scale rating with a classification between the Mohs rating of 1- 4.5 and the other between the range of 7.5 – 9. It is also important to note that the Mohs Scale gradation is exponential, which makes most drill bit range in 1-4.5 range meet the requirement for most core bore bits. Another thing to consider for bit selection, which also on the comparison chart, is the bit geometry.

Core Bit Grades
Figure 3: Core Bit Grades

3.Core Bore Bit–Rate of Penetration

The rate of penetration (drill speed) is the speed with which the core bore bit penetrates the surface you are cutting. Different factors determine and support the penetration of the core bore bit. Top of which are drill pressure, bit sharpness, bit formula, and surface hardness.

A standard core bore bit penetrates at a rate range of 2 inches per minute to 12 inches per minute. However, note that this may be different for harder surfaces. As surface hardness increases, it is best to reduce the penetration rate to help increase bit service life.

Now, this penetration rate is mainly affected by the diamond core bit geometry. Different manufacturers come up with different bit geometry, and all of this individual geometry cut differently. You can view it in a way to mean that different geometry for different penetration levels of a surface.

There is a base type of core bore bit geometrical configuration, namely the standard configuration. This geometrical configuration permits an increased amount of fluid circulation, mostly from the outside to the inside diameter. This particular geometrical design is very popular among operators today because of its efficiency. It is from this standard bore bit configuration that manufacturers manipulate to achieve more effective core bore bits with higher penetration.

Penetrating Core Bit
Figure 4: Penetrating Core Bit

4.Drilling Depth

Another important consideration for your choice of diamond core bit is the drill depth. In response to having a more effective cut at extended depths, manufacturers design diamond core bits with different levels of impregnation. The impregnated diamond core bit has grown to be one of the most popular in the industry today. The impregnated diamond model has superior advantages compared to other core drill bits, some of which are;

i.Wide range of application: the impregnated diamond has a broader range of use due to its strength and superior resistance to heat. It makes them the perfect tool for cutting hard or abrasive surfaces.

ii.Geometry: the structural design of the impregnated diamond core bit makes it more resistant to damage in the hole when drilling.

iii.Multilayer diamond arrangement: It gives a bit long service life. It also makes them the best choice for tough surfaces.

That said, the different levels of diamond impregnation will indicate how deep a diamond core bore bit can drill. Core bore bits with more levels of diamond impregnation are drilling further than those with lesser levels of impregnation.

Another essential factor support extended depths is lubricity. Friction emanating from the contact of the surface to cutting edge of the bit is a primary challenge that core bit users face. For continued and sustained drilling, your drill bit must have a constant water supply for lubrication. It is the reason why most users opt for wet core drilling instead of dry core drilling.

Most wet core bore bit has a constant flow of water that helps the drill to pierce through the surface. The water as a lubrication mode doesn’t just make the bit travel longer, and it also makes it travel faster. In the end, the wet core drilling will leave you with a neater job compare to the dry core drilling.

Deep Drilling
Figure 5: Deep Drilling


Using diamonds in your cutting tool already set the price far away from the sights of other drill bits. So, the level of impregnation you have will tell how expensive your core bore a bit. Furthermore, the different geometrical configuration also makes the core bore a bit more costly as manufactures are always optimizing and looking for the custom-made core bore bits that meet penetrates and cuts better.

Now, please don’t get carried away to think the most expensive bit is usually the best, not so really. You would first carry out a scratch test on the surface to know the hardness, which will help decide the bit use. As such, you may not necessarily need the bit with the highest impregnation to have an effective cut. Instead, you will choose that will is useful both in cutting and from an economic standpoint.


A core bore bit is a cutting tool that is popular among professional, skilled users and unskilled users. The different terrains that most operators find themselves in will require some particular characteristics from the drill bit. This article outlays the different tips for choosing the core bore bit.

Therefore, as you continue to look out for helpful tips to choose the core bore bit, look no further, NCCuttingtools has got you covered. They can provide you with corresponding services due to their numerous years of experience. Click for a video with up-to-date information about the core bore bit.

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