Keep drilling until the core drill teeth hit the surface of the wall. You will feel them bite once they do. 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. 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. 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.

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. 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. 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 To do this they should be used in short bursts and the whole bit should be regularly withdrawn from the hole and exposed to the air to disperse any heat.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.

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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! Unlike carbide drill bits, the teeth on a diamond core bit features diamonds that are embedded in the teeth themselves. As diamonds are extremely hard they grind their way through the surface you’re working on creating a sharp and clean cut. Once you have cut 25-30mm into the surface you are working on, you can withdraw the core bit and remove the guide drill and carry on without it. 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 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 your drilling you should always make sure there are no cables or pipes hidden in the wall at the spot you intend to drill your hole. The best tool to use for this is a cable and pipe detector. You simply pass it over the surface of the wall and if any items such as these are found, lights and/or a buzzer indicate their presence. How to Drill a Hole using a Core Drill 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.

With the above in mind, dry cutting diamond core bits are generally used when working indoors, whereas wet cutting bits are used externally. 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. For example, smaller holes up to 30mm in diameter can be drilled at up to around 3000 rpm whereas large holes around 400mm should be drilled at speeds as low as 300rpm. There are many core drill sizes and generally each size is manufactured to represent the size of a commonly used pipe, cable or duct so that once the hole is drilled, the object in question passes through with ease.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. Corded power drill with safety clutch and variable speed ideal for use with a core drill How Fast Should you Drill When Using Core Bits? Most domestic use diamond core cutters will always have a removable guiding drill bit which acts as a pilot hole to guide the core drill. 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.