Roller-cone bits: These bits have three cones with teeth that rotate and grind the rock, allowing the bit to penetrate the formation. Roller-cone bits are commonly used in oil and gas drilling. PDC bits: PDC stands for polycrystalline diamond compact, which is a type of superhard material used in the cutting elements of the bit. PDC bits are commonly used in geothermal drilling and some oil and gas drilling applications. Diamond bits: These bits use industrial diamonds as the cutting element, which allows them to drill through very hard materials such as granite or basalt. Diamond bits are commonly used in mining and geothermal drilling.