Abstract: A stamping tool for use in an auto-indexable tool station having a number of character inserts that can be rotatably moved below a striker area so that a thin metal plate or sheet of metal may be marked. The stamping tool allows for automatic adjustment of tool length for any variation in material thickness. A pneumatic cylinder actuates a mechanism that engages the key way in the head nut. The tool length is changed by the rotary motion of the auto-indexable tool station. The character housing is rotated by the indexable tool station through the punch key which moves the selected character insert to the striker area within the tool. The striker area causes the character insert which is spring biased to protrude lower than the character inserts that are not in the striker area. When the stamping tool is struck by the ram, only the character insert in the striker area will contact the material to be marked.