Drill bit

Drill bits are the cutters of drill tools. Bits are interchangeable, meaning that they can be removed from the end of the drill, either to replace a worn part or to change the size of the part.

Diamond core drill

Diamond core drill bits are used to bore large holes in brick, concrete and stone. They are not generally used in other materials. The bit consists of a metal cylinder, usually relatively soft steel mounted on an arbor. Industrial diamonds are embedded at the open end of the cylinger. In the image, the diamonds are on the metal segments attached to the end. The segments are thicker than the cylinder wall, so most of the bit does not rub in the hole being bored. The sloping slots in the cylinder wall help carry the dust out. Diamond core drills can be used with or without water lubrication. The drill shown can cut a 115 mm diameter hole through a single-thickness brick wall in less than a minute, running at about 300 RPM. The resultant hole is very cleanly cut.

Related Topics:
Brick - Concrete - Stone - Steel - Arbor - Diamonds - Lubrication

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This form of core drill wanders hopelessly when presented to a flat surface, and needs a centring mechanism. The arbor can carry a drill bit to bore a centring hole, but the version shown has a plain 10 mm rod. A 10 mm masonry twist drill must first be used to drill the centring hole for the rod. A wooden or stone template, a close fit for the cylinder, can also be used to guide the bit at the start of the cut. After the first few millimeters of cut, the centring mechanism may no longer be needed, although it will help the bit to bore without wandering in a deep hole.

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Diamond core drill bits for use with portable drills are commonly available in diameters from 20 mm to 130 mm. The only limit on length of the cylinder, and thus depth of the hole, is the need to remove the bit from the hole to clear dust. 300 mm cylinder length is not uncommon, although shorter bits are usual.

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