Method enabling a command to switch the measure mode to be entered in a single vertical axis dimension-measuring column. The mode witch command is entered by pressing the probe tip against the piece to be measured during a time interval greater than a predetermined value. The measuring and displaying system then engages in a search mode of the turn-back point of said piece to be measured. Application: measurement of inner or outer diameters by means of a single-axis measuring column. The method allows the hole's minimal and maximal points to be determined with a minimum of handling operations.