Patent ID: 7849939

Claim:
A drill bit suitable, in use, for producing a hole, comprising: a main body having an axis about which it is rotated in use, a cutting face, the movement of which, in use, across the surface of the material to be cut causes material to be gouged or scraped away, a connecting mechanism for, in use, attaching the bit to a source of rotary motion, said connecting mechanism also enabling the imparting of a force on the bit such that its cutting face is urged onto the material to be cut, a gauge region intermediate said cutting face and said connecting means, said gauge region comprising at least one member movable between a first position in which the gauge region is bounded by a hypothetical tubular surface of constant cross-section co-axial to the axis of rotation; and a second position in which a portion of the member is located radially inwards, with respect to the axis of rotation, of its position when said member is in said first position, the gauge region whilst said member is in said second position being bound by a hypothetical three dimensional conical sectional surface; at least one actuator, each said member being mechanically linked to an actuator such that each member can be moved between said first and second positions by a said actuator; wherein said actuator is actuated by a control signal in response to the desired path of the drill bit such that said member occupies said first position whilst the drill bit traces a substantially straight path and said member occupies said second position whilst the drill bit traces a curved path.