... saws or diamond core drill bits. They are used to drill glass, ceramics, ceramic tile, porcelain, porcelain ... drill bit is that is only drills out a small portion of the hole - about 10% compared to a ... however, in very hard materials, they are preferable to solid bits for even small sizes.Technically, core ... Core drills are measured by the inside diameter, which is the "core size" of the "plug" that ...