Types of Drill Bits for Granite

Diamond Core

• Drill bits with diamond cores can withstand the pressure and heat that come with drilling through granite. Typical concrete drill bits will not be able to bore through granite since concrete is much softer. Also, drilling through granite produces much friction and heat, because of its hard surface. Some drill bits are coated with diamond powder to help keep them strong; these are called blunt nose bits. Core drill bits drill a smaller hole inside the outer core; these tend to drill much faster than blunt nose bits since they only drill a small portion of the granite, and not entire holes.

Diamond Alternatives

• Drill bits that do not use diamond powder on their surfaces sometimes use black oxide coating to help the bit withstand pressure and increase its strength against the granite slab. The coating also acts as a lubricant to help reduce friction and reduce heat. Tungsten carbide tips are the second-toughest tips next to the diamond ones, which make them a good alternative to diamond core bits.

Hammer Drill Bits

• Hammer-type drill bits use varying speed settings to "hammer through" granite, as compared to regular, fixed-speed drills often used with diamond core drill bits. Hammer drill bits have blunt edges, which punch through the material in rapid succession. For softer, more brittle materials, this helps the drill bore a hole much faster. For granite, this hammering action minimizes friction and heat from the drilling process. Some drills have a non-hammer and hammer-type mode built into the drill, which the user can switch on or off, depending on his drilling needs.

Wet and Dry Drill Bits

• Two types of drill bits behave differently when dealing with friction. Dry bits just drill or hammer a hole into the granite without producing or allowing any type of moisture to cool the surface. In some cases, the black oxide coating is the only form of lubricant. Wet drill bits have water contraptions that allow for the constant flow of water while drilling, which helps lower the temperature of the material while a hole is being drilled.