Abstract: The device for inserting polygonal and shaped bars in the collet of the chuck of machine tools comprises a bar pusher element arranged inside a bar guiding channel and a motor element connected to a worm screw which cause sliding of a slider rigidly associated with the bar pusher. The device has a spring mounted in abutment against the worm screw and adapted to be compressed when the bar rests frontally on the collet of the rotating chuck, so as to absorb the thrust of the motor and to press the bar against the collet, and a motor switch activated by the compression of the spring until the rotation of the chuck causes the chuck to be brought angularly in step with the bar and the bar to be inserted in the collet.