It's been stated more than once that the fillet (filler thickness) should be 3 times the thickness of the tubes being joined. My question is where the "thickness" is measured. We are talking bronze brazed here.

Assuming you are joining two tubes of .9mm wall, the thickness of the filler would be less tan 1/8". Or do you combine the two tubes (1.8mm) and times the thickness times three (approx. .211")?

In either case, if the "filler" thickness is measured at it's "fattest" point it appears to be a much smaller fillet than what I see the "fillet pros" doing, assuming they provide a consistent radius at the joint.

Does this mean (assuming the 3x number is correct) we can get by with smaller fillets than we commonly see?