| 摘要 |
A drill bit for use in drilling a well bore comprises a main drill body (l0) adapted to be rotated about a substantially vertically disposed axis of rotation (20) 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 (34, 36, 38) are mounted on the outside of the main drill body (10) at equally spaced locations, with the cutting discs each having cutting elements (35, 37, 39) disposed in a ring-shaped array. Each of the cutting disc (34, 36, 38) 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 (34, 36, 38) is slightly offset laterally in a rearward direction from the centerline (20) of the main drill body (10), 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 (34, 35, 38) to be positioned to be particularly effective and aggressive in cutting the well bore.
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