Abstract: An automatic numerically controlled machine tool or "bed machining center" presents a tool carrying spindle rotating in a vertically movable head sliding on a forwardly and rearwardly movable column, for cutting tool engagement with a workpiece clamped on a laterally movable table. The head, the column and the table are slidingly movable by precision ball screws on mutually perpendicular way members, accurately positioned with pivoting fine adjustment. Sliding ramp gib pack cam block pairs further adjust the sliding members for maximum precision. Replacement spindle and vertical ball screw assemblies are easily substituted for rapid maintenance. High volume coolant circulation flushes chips away from the workpiece. A concealed tool change carriage glides forward from an enclosure, receives the previous tool from the spindle, indexes the next tool, releases it for automatic loading in the spindle collet, and retracts into its enclosure.