The ideal clearances between tubes, for brazing, for good capillary action has been mentioned as 0.05mm to 0.200mm. What should be the depth of insertion?
The depth of insertion gets automatically determined when a correct swaging tool is used to swage the end of a tube which is to be brazed to another of the same size. It is usually kept equivalent to the OD of the tube. It is possible to also braze a smaller tube of 1/4″ to a bigger tube of 3/8″ tube without any swaging. However the clearance between the tubes becomes much higher than the permissible 0.200 mm and here the insertion has to be longer (about 0.75 to 1 inch) and a brazing rod with 15% Ag and 5% P has to be used even for Cu to Cu brazing. However when brazing a 3/16″ Cu tube to a 1/4″ Cu tube it will be necessary to swage the end of the 1/4″ tube, as otherwise, the clearance between the tubes becomes too small (0.025mm).
