DRILLING APPARATUS WITH A RADIALLY DISPLACEABLE REAMER AS WELL AS A REAMER AND A PILOT BIT

摘要

A drilling tool for boring in earth and rock formations includes a pilot bit which defines a longitudinal tool axis and includes a cam part having a cam axis arranged eccentrically relative to the tool axis. A reamer includes a hollow reamer body mounted on the cam part for rotation relative thereto abo ut the cam axis. 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 carries cutting elements fo r enlarging a hole drilled by the pilot bit when the reamer is in its extended position. The cam part carries a first removable insert on which a first sto p surface is formed. The reamer carries a second removable insert on which a second stop surface is formed. The stop surfaces are engageable with one another when the reamer body is radially extended, for transmitting rotation al cutting forces to the reamer. The stop surfaces are formed of a material harder than a material from which the cam part and the reamer body are forme d. The stop surface of the insert carried by the reamer may be formed by a plurality of rotary ball bearings.