Abstract: A machining center or machine tool comprises a bed, structure to support and position the workpieces, and a rotary spindle fed with worktools by an automatic tool changer and carried by a spindlehead which also carries the driving motor therefor. The spindlehead moves back and forth along a rectilinear path under the control of a circulating-ball screw and nut assembly, the screw of which is rigid with the spindlehead and has its axis intersecting that of the spindle. The lead nut of the same assembly is caused to rotate by a motor and is kept axially fixed.

Abstract: A machine tool, designed for volume production, comprises a head with a single spindle, rotatably mounted about an axis, inclined by 45.degree. in respect of the horizontal working plane of the machine. Automatic control means allow said head to take up at least the two positions corresponding to the horizontal spindle position and to the vertical position, while a single device is provided for the automatic change of the tools, adapted to change the tools on the spindle of said head, when the latter takes up one of said two positions.