Internal milling machine for milling crank pins

In an internal milling machine for milling crank pins on a crankshaft, said machine having a fixed frame, a milling cutter holder mounted on said frame for horizontal and vertial movement within a vertical general plane, an internal milling cutter mounted in said cutter holder for rotation about a cutter axis normal to said vertical general plane, chuck means mounted on said frame for supporting a crankshaft in an operative relationship to said cutter wherein said crankshaft projects axially through said cutter with the crankshaft axis normal to said general plane, and orbiting means for driving said cutter in orbital milling movement around a crank pin of a crankshaft supported in said chuck means;

• the improvement wherein said orbiting means comprises a main shaft mounted on said frame for rotation about a shaft axis normal to said general plane, cam roller means mounted upon said main shaft for rotation with said shaft and for rotation about a cam axis parallel to and radially offset from said shaft axis, a first cutter holder shifting means including a follower surface engaged by said cam roller means for transmitting vertical movement of said cam roller means relative to said frame to said cutter holder, second cutter holder shifting means including a follower surface engaged by said cam roller means for transmitting horizontal movement of said cam roller means relative to said frame to said cutter holder, and drive means for driving said main shaft in rotation about said shaft axis.