Abstract: A method for forming collars in a thermally conductive plate is provided. The method includes the steps of placing a thermally conductive plate, or fin stock, within a press, and then advancing the plate through the press in order to draw a desired amount of ductile material from a plurality of collar locations within the plate. The ductile material is used in forming the collars. The method also includes further advancing the plate in order to pierce the material at the collar locations, thereby creating a plurality of through-openings in the plate. Each through-opening defines a radial wall having a proximal end and a distal end. The press is used to fold material at the distal end of the respective walls inwardly into substantial contact with an inner diameter of the walls. In this way, a plurality of collars having a first flare are formed. The material is further advanced through the press so that the distal ends of the collars are flared outwardly, thereby forming double flare collars.

Abstract: A collar for a fin-tube heat exchanger is provided. The collar extends outwardly from a thermally conductive plate in order to receive a tube. The collar generally includes a wall having a proximal end integral to the conductive plate, and a distal end defining an opening configured for receiving a tube. The wall includes a reflare portion at its distal end, with the reflare portion being curled into either the inner diameter or the outer diameter of the wall. Preferably, the reflare portion is curled into the inner diameter of the wall, and then further flared outwardly to form a double flare. A method for forming the double flare collar is also provided. The method involves progressively moving fin stock through a metal-stamping machine in order to sequentially form double flare collars.