Machine tools

There is disclosed a tool storage and changing mechanism comprising a rotatable table tool rack having radial sockets to removably hold toolholders, a horizontal arm, forming a track between the tool rack and the machine spindle, carries a mechanical hand having a forked end to receive from the rack and hold a selected toolholder and carry it to and from the spindle. Assuming that the work with the toolholder has been performed, the empty hand travels to the spindle where, without vertical movement of the arm, the hand grasps the toolholder in the spindle which then releases the toolholder. The arm and hand then descend to withdraw the toolholder from the spindle, after which the arm rises again and the carriage travels back to the rack and deposits the toolholder in its rack socket. When the tool rack is indexed to bring the next tool to the hand, the hand engages the tool and with it approaches the spindle, the arm descends, and, when the toolholder is substantially vertically aligned with the spindle, the arm rises and inserts the toolholder in the spindle where it is grasped by the spindle. Then, without descending the hand is withdrawn from the toolholder and returns empty to the rack. The arm and hand are operated by mechanism including a reversible motor and the above operations are performed in two successive continuous steps, the second being the reverse of the first and resulting from a change in the direction of operation of the motor made between the two steps.