Abstract: A method of manufacturing a heat exchanger coil, the method comprising the steps of reconfiguring the cross-sectional shape of an elongate tube from a substantially round cross-sectional shape having a first outer circumference to a reduced or corrugated cross-sectional shape having a second outer circumference which is less than the first outer circumference, forming a plurality of u-shaped hairpin tubes from the elongate tube, the u-shaped hairpin tubes each having a pair of parallel legs, inserting each of the parallel legs of the hairpin tube through a predetermined opening in at least one fin plate, attaching a plurality of return bends to the u-shaped hairpin tubes to form a predetermined circuitry and then incrementally applying fluid pressure from a fluid pressure source to an internal channel of the circuitry to incrementally expand the circuitry to form a tight heat transfer bond between the circuitry and at least one wall of the predetermined opening.

Abstract: Method and apparatus is disclosed for severing flat tubing. A length of tubing is gripped at longitudinally spaced apart locations and the tubing is deeply scored by rapidly rotating circular cutters which are moved across the faces of the tubing at a predetermined linear velocity. The angular velocity of the circular cutters greatly exceeds the linear velocity of traversal. An axial force is applied to separate the tubing.

Abstract: Method and apparatus for separating thin-walled flat metal tubing are disclosed. The tubing has flat upper and lower walls joined by end walls. The tubing is partially severed by providing relative movement between the tubing and opposed cutting blades having straight or slightly curved cutting edges. The relative movement is transverse to the longitudinal axis of the tubing, and the straight slicing edges, or the chords of curved slicing blades, form a small acute angle with respect to the flat faces of the tubing. The tubing is completely severed by applying an axial force to the tubing. Pressing heads follow the slicing blades to press any burrs back into the tubing.

Abstract: Method and apparatus for separating thin-walled flat metal tubing are disclosed. The tubing has flat upper and lower walls joined by end walls. The tubing is partially severed by providing relative movement between the tubing and opposed cutting blades having straight cutting edges. The relative movement is transverse to the longitudinal axis of the tubing, and the straight cutting edges of the blades form a small acute angle with respect to the flat faces of the tubing. The tubing is completely severed by applying an axial force to the tubing.