A notched scale placed at right angles to the movable wire of a filar micrometer, and designed so that one turn of the micrometer screw will move the micrometer wire across one notch of the scale. The central notch of the comb, in conjunction with the zero of the micrometer head, furnishes a fiducial point from which all readings are reckoned. The comb is used for keeping count of whole turns of the micrometer screw; parts of turns are read on the graduated head of the micrometer.