Down reaming apparatus

摘要

A down reaming apparatus including a cutterhead body and a plurality of arms radially disposed on the cutterhead body with cutter assemblies on each arm. A first arm has a given length and additional arms each are of different length. Arm extenders having cutter assemblies are attached to each arm such that the combined length of each of the arms and attached arm extender is substantially equal. Spacers are attached to at least one of the arms to increase the diameter of the cutterhead in conjunction with the relocation of each of the arm extenders.