Questions for the group; I see many folks online, Insta, etc. that do a fusion pass and then a filler pass. Why make two passes? Why not just do the filler pass first and call it good? Is the fusion pass necessary?
I have been welding at work quite a lot and we don’t ever do fusion passes if we can avoid it. Granted it’s not bicycle tubing (usually 18 gauge sheet metal), but it got me thinking.
Thanks.
Brandon
I’ve only see that done in Ti. Is that the material you’re talking about?
TIG welding with silica bronze is a lot of fun. I’ve done a lot of it, though never in bicycle frames…
I know this a very old post and probably nobody is much interested any more, but I just joined and am on my way to scrolling to the bottom 
TIG brazing probably is strong enough in fact. The UTS of the filler rod is only slightly less than mild steel but you have a thicker fillet. I have tried destruction-testing it on test pieces and it is very nearly as strong as a weld. However I still don’t use it on the main joints of the frame, just in case, and because there’s no reason to.
I do however use it for bridge tubes, because my priority there is not to compromise the tube I’m joining to. Again welding is absolutely fine, but you’re putting a bit less heat in if you braze these. I also use it for attaching bottle bosses and cable guides etc. Most people silver solder those I know but I use the TIG for everything.
I have also used it on a couple of “raw finish” frames on top of a regular TIG weld for a fake fillet-brazed look.