What are core bits? Core bits are cutting tools used to remove a cylindrically shaped piece of material, called a core. Core bits have a hollow center, similar to hole saws, but differ in application. A hole saw is meant to create a large hole in a workpiece, while a core drill is designed to cut a hole and remove a core sample or to drill a hole without leaving material behind. Diamond core bits have diamond cutting tips and are frequently used for drilling in materials such as concrete, stone, and asphalt. This type of bit can also be manufactured as wet or dry type bits. Wet core bits are used with water, while dry used bits can be used dry. Rotary core bits are used in downhole drilling applications. The hollow center in which the core is contained is called the barrel. Rotary core bits contain an inner and outer barrel, separated by ball bearings, which allows the bit to rotate while the core in the inner barrel remains stationary.