Abstract: The present invention is a method and apparatus which accurately predicts one or more operating characteristics of an earth boring drill bit operated under a set of known operating conditions. A range of operating conditions may be input so that the operating characteristic(s) of the drill bit may be predicted over, and perhaps beyond the range the drill bit designer has anticipated. In this manner, a new drill bit design may be refined and/or proven with a high level of confidence prior to manufacture. Only minimal field testing of the new design is required to verify its performance.

Abstract: A method of determining characteristics of a rotary drag-type drill bit comprises the steps of: creating a computerized representation of the cutters on the drill bit, and then, with each cutter in turn, projecting the shape of the cutter onto a fixed plane having an array of cells, and assigning a first marker to those cells of the array which overlie the projection of the selected cutter. The representations of the other cutters are then rotated about the bit axis until they have all passed through the plane at least once, the cutters also being moved axially while being rotated so as to represent the axial movement of the bit during drilling. The shapes of the other cutters are projected onto the plane, as they pass through it, and a second marker is assigned to those cells of the array which overlie both the projection of the selected cutter and the projections of any of the other cutters.

Abstract: A torque transmitting device for use with a rotary drill bit connected to a drill collar, comprises a first member connected to the drill collar, a second member connected to the drill bit, and coupling means connecting the two members together for rotation about a common central axis. The coupling means permits limited relative rotation between the members about the axis, but provides a resistance to rotation of the first member relative to the second member in a forward drilling direction which is greater than its resistance to relative rotation in the reverse direction. The comparatively lower resistance to rotation in the reverse direction prevents momentary reverse rotation of the drill collar, due for example to torsional oscillations, being transmitted to the drill. bit. This reduces the likelihood of damage to the cutters on the drill bit, which might otherwise result from such momentary reverse rotation of the bit.