Abstract: An apparatus for forming phosphor layers in cathode-ray tubes includes a table having a plurality of operating positions for processing panels for cathode-ray tubes to coat phosphor layers thereon. A plurality of angularly spaced clamp heads for holding the panels, respectively, are supported on the table for rotation about a first axis and angular movement about a second axis in each of the operating positions. A cam, which is operatively connected to the clamp heads, has a first cam groove for angularly moving the clamp heads through different angles about the second axis in the operating positions and a second cam groove for keeping the clamp heads in a fixed angular position with respect to the second axis in the operating positions. Joint cam groove mechanisms are combined with the cam for selectively switching between the first and second cam grooves.