Rotary drill bits exhibiting sequences of substantially continuously variable cutter backrake angles

摘要

A rotary-type earth-boring drag bit with cutters oriented at varied rake angles. Specifically, cutters that are located sequentially adjacent radial distances from a longitudinal axis of the drill bit have cutting faces that are oriented at rake angles that differ from one another. These cutters may be located on the same blade of the drag bit or on different blades of the drag bit. The rake angles at which the cutting faces of these cutters are oriented may be based, at least in part, on the relative radial distances these cutters are spaced from the longitudinal axis of the drag bit, on the vertical positions of these cutters along the longitudinal axis of the drag bit, or in response to actual or simulated evaluations of the use of drag bit to drill a subterranean formation. Methods for designing drag bits are also disclosed.