LollyKat wrote:David9694 wrote:When you say welded, do you mean fillet brazed?
Not being an engineer I'm not too sure of the difference . I meant lugless.
Put simply brazing is used as a glue that runs in to a tiny gap between adjacent surfaces. Welding is a join that melts the adjacent faces together.
531 could be built with lugs or lugless brazed. If the latter it was important that the tubes were cut and finished to produce a perfect mating surface and a strong joint. This can involve a lot of time filing by hand.
631 can be welded so the builder can save time and expense on the tube interfaces by just cutting to shape and letting the weld bridge the imperfections.