Lathe with a polygon machining device

A lathe comprising:

• a machine body including a spindle that is journalled thereon, and a chuck that is adapted to hold a workpiece to be machined;
• a transverse rail member disposed slidably on said machine body and extending in a transverse direction relative to said spindle, said rail member being movable on said machine body along a longitudinal direction of said spindle;
• a cutter carrying plate disposed slidably on said rail member and movable along a longitudinal direction relative to said rail member;
• a turret unit attached to said carrying plate and adapted to lathe the workpiece;
• a polygon machining cutter unit attached to said carrying plate and spaced apart from said turret unit in the longitudinal direction of said rail member, said polygon machining cutter unit being adapted to form a plane on the workpiece;
• a cutter shaft attached fixedly to said polygon machining cutter unit and disposed parallel to said spindle;
• a rigid driving shaft journalled on said machine body and disposed parallel to said spindle;
• a driving source for rotating said spindle;
• a clutch device movable between a connecting position, where rotation is transferred between said spindle and said driving shaft so as to rotate said driving shaft, and a disconnecting position, where rotation of said driving shaft is stopped;
• a rigid driven shaft journalled on said machine body and extending in the transverse direction relative to said spindle;
• a first gearing interconnecting said driving shaft and said driven shaft and movable on said driving shaft for transferring rotation from said driving shaft to said driven shaft;
• and
• a second gearing interconnecting said driven shaft and said cutter shaft and movable on said driven shaft for transferring rotation from said driven shaft to said cutter shaft.