A method of forming a ducting assembly with flanged end connectors for use in heating, ventilating and air conditioning, comprising:
- (a) forming rectangular or square cross-sectionally shaped ducting with rounded corners from thin gauge metal, comprising:
- (i) pre-forming round cross-sectional ducting from thin gauge strip material having side edges by using a continuous forming method to form a helically wound spiral seam tube with the edges of the thin gauge strip material interlocked together, said round cross-sectional ducting defining a circular-shaped interior;
- (ii) placing the pre-formed spiral seam tube over an expansion die comprising opposed die members, both of said die members each having an outwardly directed face and side edges substantially perpendicular to the outwardly directed face with the intersection of the die member faces and corresponding side edges defining rounded corners;
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- (iii) forcing the die members away from each other to bear against adjacent portions of the interior of the pre-formed spiral seam tube so that the pre-formed spiral seam tube transforms into a substantially rectangular or square cross-sectional shape, said rectangular or square cross-sectional shape composed of straight sections defined by the outwardly directed faces of the die members and rounded corners defined by the rounded corner intersections of the die faces with the side edges of the die members;
- (b) forming flanged connectors having an insertion section and a mating flange section, comprising:
- (i) notching a length of strip material to remove portions of the strip material corresponding to the insertion section and corresponding to the mating flange section, thereby to define corners of the flanged connector;
- (ii) forming the strip material into a desired cross-sectional shape, said cross-sectional shape comprising the insertion section to engage within or over an adjacent end portion of the ducting and the mating flange section disposed substantially perpendicular to the insertion section for mating with the mating flange section of a corresponding flanged connector;
- (iii) bending the formed strip material at the notches to define a shape corresponding to the cross-sectional shape of the ducting to be interconnected wherein the mating flange portion extending around the insertion section;
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- (iv) affixing end portions of the bent and formed strip stock together to form a closed flanged connector corresponding to the cross-sectional shape of the ducting;
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- (c) assembling the flanged connectors to the ends of the formed ducting.