Abstract: A drill bit characterized by a body fitted with multiple, spaced blades having a forward sweep relative to the center of the bit and cutting elements embedded in the blades at a selected back rake and side rake. In a preferred embodiment the cutting elements are cylindrical and are shaped to define first and second bevelled cutting edges disposed at selected bevel angles with respect to the sides of the cutting elements. The cutting elements are strategically located in the respective blades in desired forward sweep, back rake and side rake configurations to facilitate optimum cutting efficiency and channelling of drilling fluid pumped through the drill bit around the blades and cutting elements to clear the cutting elements of formation cuttings in an optimum manner.

Abstract: A core drill bit having a nozzle screen and designed for drilling into an underground formation and obtaining samples of the formation. As the bit cuts through the formation, a core of the formation material is forced upwardly through the drill bit into the attached core barrel and drilling fluid is pumped from the surface, through the core barrel and the screen mounted in the body of the bit and subsequently, through jet nozzle orifices radially arranged in the crown of the bit. The screen prevents oversized formation fragments, gravel and debris from lodging in the jet nozzles and obstructing the nozzle orifices and thus facilitates unobstructed flow of drilling fluid through the jet nozzles.