Image Number 4 for United States Patent #7958953.
A bi-center drilling tool comprises a main reamer region located eccentrically to an axis of rotation of the tool, and a leading cutting structure located ahead of the main reamer region, in the drilling direction. The leading cutting structure is located so as to apply a side loading to the drilling tool. The side loading is in direction to counter the loading which, in use, is due to the main reamer region being eccentric to the axis of rotation.
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