Abstract: A tool head or “head assembly” having on-board logic (1) for being mounted on a rotatable spindle of a machining center, as a boring machine, (2) for being rotated about a primary axis of spindle rotation (PRA), and (3) supports a tool as a boring bar at a controllable radial offset distance (ROD) from the PRA. The PRA aligns with the axis of a workpiece bore being formed The head advances along the PRA and rotates in a boring operation. As the head advances, the ROD of the tool is controlled by a micro-controller and secondary logic on-board the head cooperating with primary logic in a remote controller to provide a complex multi-diameter workpiece bore configuration. Rotating head elements protectively surround the secondary logic and control elements that regulate the ROD and may compensate for vibration, wear, and backlash. The head is usable with spindles of diverse machine tools.