Abstract: The present invention relates to a system for attaching a tool holder to a machine tool which includes an automatic hook-up of an electrical, pneumatic or hydraulic connector to supply power to the tool holder. The system includes an attaching sleeve slidably mounted on the tool holder mounting stud. A spring interposed between the mounting stud and the attaching sleeve exerts a biasing force on the attaching sleeve. The power connector is separable and has a portion attached to the machine tool and a mating portion movably attached to the tool holder. A pin interconnects the attaching sleeve and the movable mating portion of the connector.