Patent ID: 6112835
Filing Date: 2000-09-05
Classification: E21B

Abstract:
A drilling apparatus for boring in earth and rock formations, comprising:a pilot bit defining a longitudinal tool axis and including a cam part having a cam axis arranged eccentrically relative to the tool axis;a reamer including a hollow reamer body mounted on the cam part for rotation relative thereto about the cam axis, whereby relative rotation in one direction causes the reamer to be radially extended, and relative rotation in an opposite direction causes the reamer to be radially retracted, the reamer body carrying cutting elements for enlarging a hole drilled by the pilot bit when the reamer is in its extended position; andfirst and second stop surfaces disposed on the cam part and the reamer body, respectively, and engageable with one another when the reamer body is radially extended, for transmitting rotational cutting forces to the reamer body during a boring operation;the first and second stop surfaces disposed on respective first and second removable inserts that are removably mounted on the cam part and the reamer body, respectively, the first and second stop surfaces being formed of a material harder than a material from which the cam part and the reamer body are formed;wherein the pilot bit includes a drill head rigid with a lower end of the cam part, the reamer disposed above the drill head and being rotatable relative thereto.