Machining unit with orientable spindle-axis for milling and boring operations

A machining unit, comprising:

• a fixed base,
• a first lower side, slidably mounted on the base along a first horizontal direction,
• a first motor means carried by said base for controlling the position of said first lower slide along said first horizontal direction,
• a second upper slide, slidably mounted on said first lower slide along a second horizontal direction perpendicular to said first horizontal direction,
• second motor means carried by said first slide, for controlling the position of said second upper slide along said first horizontal direction
• a spindle-carrier structure mounted on said second slide and defining a spindle axis substantially parallel to said second horizontal direction,
• a tool carrying spindle, rotatably mounted within said spindel-carrier structure, and driven by a motor carried by said spindel-carrier structure, said spindle having a front end which is selectively coupable to a milling tool or a reaming tool,
• means for supporting a workpiece at a fixed position relative to said base, with the workpiece having a planar surface located in front of said end of said spindle and substantially perpendicular to said second horizontal direction, said planar surface being to be subjected to a milling operation with the aid of said milling tool and/or to a boring operation with the aid of said reaming tool,
• wherein said spindel-carrier structure is freely pivotally mounted relative to said upper slide around a vertical axis intersecting said spindle axis, by means of a vertical hinge pin, said spindel-carrier structure being received within a cradlelike support surface of said upper slide which is arranged so as to allow a slight rotation of said spindel-carrier structure around said hinge pin, while always supporting the spindel-carrier structure, and
• means for controlling the position of said spindel-carrier structure around said hinge pin, comprising actuator means connected to a portion of said spindel-carrier structure spaced away from said hinge pin, so that activation of said actuator means causes a slight rotation of said spindel-carrier structure around said hinge pin, and
• means for locking the rotation of said spindel-carrier structure relative to said upper slide around said vertical hinge pin either in a first position, in which the axis of the spindle is orthogonal to said planar surface of the workpiece, for a boring operation, or a second position, in which the axis of the spindle is slightly inclined with respect to said orthogonal direction, for a milling operation.