Again, as we have also touched on above, there are several different types of core bit available and depending on the object you are drilling through and the size of hole you need to create will ultimately depend on what type of core drill your should use. Carbide Core Drill Bits When using dry cutting bits it is essential that they are kept as cool as possible. To do this they should be used in short bursts and the whole bit should be regularly withdrawn from the hole and exposed to the air to disperse any heat. Despite this, dry cutting diamond core bits don’t have to be used dry you can also use them wet. In general, a corded drill is the best to go for as it will produce power at a more constant rate, but if funds are available, the more expensive and higher quality cordless drills (minimum 24v) from brands such as DeWalt, Makita, Milwaukee etc should provide more than enough grunt.

Drilling a 6mm hole in the wrong place can easily be rectified, but trying to fill in a 4 inch hole is not an easy job at all. As well as wearing the drill bit out much faster, the hammer action also creates a lot of vibration whilst drilling often leading to the hole ending up larger than intended.If you don’t already have a suitable drill, any decent hire company will gladly supply not only the correct drill but also the correct diamond core bit, if purchasing either the drill or core bit is deemed too expensive. Remember you will also be charged for the amount of wear on diamond tipped bits. As always at DIY Doctor we advise the use of purpose built tools for DIY use. Safety must always come first. Wear the appropriate safety equipment, gloves, dust masks and eye protection at all times. If you are able to drill right the way through the wall in one go, the core drill will remove the core at exit. Before you start any drilling, the first job is to measure and mark the exact spot that you want to drill your hole so there isn’t any mistakes. Although it is not recommended, many use hammer action with these drill bits to increase their cutting speed and ability. This will ultimately wear the core bit out much faster, but as they are generally cheap this is not often seen as a major concern.

A core drill should always be used with a power drill, at minimum around 800 watts and at maximum somewhere around 1300 watts. Your chosen drill should also have a variable speed function (somewhere between 100 and 300 rpm) and it must also have a safety clutch! For the neatest cut and finish to your hole it is advisable to then finish the hole from the other side. This guarantees both a neat entry and exit hole.

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Once the core bit is attached to the arbour insert the pilot or guide drill into the arbour, pushing it in until it goes tight. Trying to drill more dense objects such as solid concrete will in most cases cause the bit to heat up, wearing it out even faster. There are in fact two different types of diamond core bit – wet cut and dry cut. Essentially, wet cut diamond core bits use water to cool them while drilling and dry diamond core bits are just used dry. Keep drilling until the core drill teeth hit the surface of the wall. You will feel them bite once they do. Essentially the speed that you drill at will be dictated to you by the size of hole you are drilling. As a very general rule of thumb, the larger the hole you are drilling and the denser the material you are drilling through, the slower the speed you should drill at.

As this point it’s a good idea to ask someone to stand on the other side of the wall and let you know as soon as the guide drill breaks through and when it does, stop drilling. With the drilling point clearly marked on the wall, next setup your core bit and drill. Screw the arbour into the end of the core bit until it’s pinch tight. Keep a close eye on your drilling depth and once you are roughly within and inch of breaking through the wall on the other side, decrease any pressure and also speed slightly.

Preparing for Drilling Holes Using a Core Drill

As we have briefly touched on, a core drill is a drill bit which cuts large holes through masonry and concrete removing the centre part of the hole (core) as it drills and cuts its way through. If you keep forcing the core cutter through, when you actually break through you will force a large amount masonry away from the outside of the hole, making a total mess of it all. At this point you will only have around half an inch or so to drill through so take your time and once done you will be left with a nice neat and clean hole.