Core drills are drills for metal that are mainly used in larger diameters (up from 12 mm). The biggest advantage of a core drill compared to a twist drill is that not all of the material needs to be cut. With a core drill you only cut the perimeter of the hole. The core (also called plug) remains intact and falls out as soon as the core drill runs through the material. Because you do not have to drill the core, you can drill much faster with a core drill than with a traditional metal drill. Another advantage is that core drills last longer as a result. Less material is cut, so there is less resistance with a longer service life as a result. Special magnetic drilling machines are required for core drilling. You can attach this drill to the workpiece (metal) with an electromagnet. The big advantage of this is that you do not have to hold the drill as with a hand drill, and that the machine can be taken along, which is not so easy with a drill press, for example. With a magnetic drill you can also drill more easily in more difficult places.