Abstract: A drill bit for use in drilling a well bore comprises a main drill body adapted to be rotated about a substantially vertically disposed axis of rotation and having therein a duct extending longitudinally along such axis, for supplying a drill fluid under pressure to the well bore. At least one generally circular, rotatable cutting discs are mounted on the outside of the main drill body at equally spaced locations, with the cutting discs each having cutting elements disposed in a ring-shaped array. Each of the cutting discs has an axis of rotation disposed at an acute angle to the vertical centerline about which the main drill body rotates. The axis of rotation of each cutting disc is slightly offset laterally in a rearward direction from the centerline of the main drill body, thus to cause the entire bit to be placed in a non-equilibrium position with the rotation of the main body enabling the cutting disc to be positioned to be particularly effective and aggressive in cutting the well bore.

Abstract: A drill bit for use in drilling a well bore in accordance with this invention comprises a main drill body adapted to be rotated about a substantially vertically disposed axis of rotation and having therein a duct extending longitudinally along such axis, for supplying a drill fluid under pressure to the well bore. Three generally circular, rotatable cutting discs are mounted on the outside of the main drill body at equally spaced locations, with the cutting discs each having cutting elements disposed in a ring-shaped array. Each of the cutting discs has an axis of rotation disposed at an acute angle to the vertical centerline about which the main drill body rotates. Importantly, the axis of rotation of each cutting disc is slightly offset from the centerline of the main drill body, thus to cause the cutting discs to be positioned to be particularly effective and aggressive in cutting the well bore.