Abstract: This invention relates to a method and apparatus for cracking off glass attached to, or comprising a portion of, the constricted end (neck) of the glass funnel component of a glass cathode ray tube and thereafter sealing a replacement glass neck component to the funnel component. A gauge and sensor mechanism are used to produce a signal representative of the location of a defined plane through the funnel. This signal is sent to a central processing unit which controls the apparatus so that the cracking off of the old neck and subsequent sealing of the new neck take place at that defined plane. In this way, the individual method steps are integrated into an automated process.