a vacuum - metallizing machine including a metal platter base having an obverse side and a face side . a substrate - receiving platter is resiliently disposed in a recess on the face side of the platter base . the platter receives a substrate to be metallized . a circumferentially - arranged rigid ring of predetermined dimensions and location is disposed on the face side and mates with a ring around a port on the wall of the vacuum chamber which surrounds an opening in the wall . engagement of these rings aligns the platter base relative to the port . a compliant ring is disposed between the wall and the platter base . the obverse side of the platter base and the chamber are resiliently forced into contact with each other with a toggling action whereby to align the platter base relative to the port , to force the outer diameter of the platter base into metal - to - metal contact with the periphery of the port , to align the substrate relative to the port and also to force the compliant ring into sealing engagement with the wall , thus , to form a vacuum tight seal .