Abstract:The function of free indexing automatic tool changer (ATC) mounted on quartet turret of CNC lathes was analyzed. The design scheme and structural features of the device to achieve cutterlocation extended on the basis of free indexing ATC were introduced, and the device was simple in structure, easy to manufacture and low cost, and easy in operation. The application results show that in the turning process of large production volume and more turning operations, productivity can be improved and cost was reduced by using the device.