Tube flare tools consist of large style tube spreaders that are used for radiator cores. The tube spreader is rolled across the tubes while pushing down to flare the end of the tube. It also consists of small tube spreaders that are used for small cores. The tube spreader is rolled across the header flaring all the tubes.
Tube flaring is a process of forming the end of a tube into a funnel shape so a threaded fitting can hold it. When a flared tube is prepared, a flare nut is slipped onto the tube and the end of the tube is flared. During tube installation, the flare is seated to a fitting with the inside of the flare against the cone-shaped end of the fitting, and the flare nut is screwed onto the fitting, pulling the inside of the flare against the seating surface of the fitting.