Diamond Core Drill Bits, also know as Diamond Hole Saws, are used to drill tile, limestone, slate, marble, granite, stone, and fiberglass. Just add water for lubrication.
Old fashioned spear point carbide bits no longer work on the new type of super-hard floor, counter and wall tiles. Diamond drill Bits are the solution.
Core drill bits have a hollow center and cut a circle in the material to create a hole. This results in a hole the size of the drill and a smaller "plug" or "core" which comes from the center. Diamond core drill bits are available in sizes from 5/64" to 4" (outside diameter). The metric manufactured size of each diamond drill bit is also available, along with the exact inch measurement.