Abstract: A core builder machine (10), including an elongated table (12) on which the cores are supported and transferred to the various assembly portions of the machine (10). A plurality of heat exchanger tubes (18) are fed from a tube magazine (16) by a tube dispenser assembly (14) onto the table (12) where they are indexed and adapted to receive a plurality of serpentine fins (36) between a pair of adjacent tubes (18) to form an intermediate core assembly (42). The intermediate core assembly (42) is transferred downstream by a plurality of slides (56, 58) to a core compression section (70) where the intermediate core assembly (42) is compressed. After the intermediate assembly (42) is compressed the header attachment mechanism (75) moves into contact with the sides (56, 58) of the core to attach the headers and form a completed core assembly (110) that can be removed and then brazed.