Diamond Core Drills are made by diamond coating one end of a metal base. Use these diamond core drill bits to make holes in a variety of hard to cut materials. Unlike conventional twist drills, diamond drills work by gently grinding (or sanding) the material you are cutting. This process takes time, you have to be patient. A core drill will cut more quickly than a solid drill since it is only cutting out a small circle of material. The larger size core drill bits will also give you a useable core, but the core from the smaller drill bits are usually destroyed during the cutting process. These tools work on all types of stone,glass,tile,composites,plastics,resins,porcelain,eggs,and much more. The smaller sizes can be used in a hand drill or rotary tool (like a Dremel or Foredom), but the larger sizes should be used in a drill press