<P> Flare fittings are a type of compression fitting used with metal tubing, usually soft steel, ductile (soft) copper and aluminum, though other materials are also used . Tube flaring is considered to be a type of forging operation, and is usually a cold working procedure . During assembly, a flare nut is used to secure the flared tubing's tapered end to the also tapered fitting, producing a pressure - resistant, leak - tight seal . Flared connections offer a high degree of long - term reliability and for this reason are often used in mission - critical and inaccessible locations . </P> <P> The tool used to flare tubing consists of a die that grips the tube and a mandrel that is forced into the end of the tube to form the flare by cold working . The most common flare fitting standards in use today are the 45 ° SAE style, and the 37 ° AN style, also used with the JIC system . The AN / JIC style generally has a higher pressure rating for a given size tubing . SAE and AN / JIC fittings are completely incompatible due to the different flare angle . Further, AN fittings (or those complying with subsequent standards) and JIC fittings are not interchangeable for design - controlled applications due to differing quality standards . The refrigeration and air conditioning industry usually uses 45 ° flare connections while hydraulic hoses are usually ​ 37 ⁄ ° flare connections . </P>

What is the purpose of reaming the tube before flaring