Originally Posted by Doug Fattic
When you say "distortion" are you saying the frame went out of alignment (all the tubes are not in the same plane) or do you mean the tubes didn't remain either round or became curved?
Hi Doug - I have bookmarked somewhere an old post of yours from the frameforum detailing the fillet brazing process, which has been a huge help in getting me to where I am, so i owe you a thanks already.
Re. distortion, I'm primarily talking about 'ovalising' the tube, eg the headtube of my last frame has a variation of about 0.25mm in it's ID. It's wider on the axial plane, which leads me to think my mitre is a touch on the loose side? This will obviously ream out when finishing the headtube, so I kinda wonder if I'm being overly pedantic?
I did have some alignment issues (headtube was out by about 0.6mm) which I put down to ill fitting mitres again, this time not getting the top tube mitres perfectly in line (they were done by hand, but that should be no excuse)
I'm using oxy propane - not sure if the lower heat therefore longer heat cycle vs acetylene has any bearing? Eg although I'm not burning the flux, it is apparent that by the time I've finished, the flux away at the edge of the heat zone is really quite dark with the buildup of oxides, which suggests too lengthy a heating cycle?
I'll maybe do a couple of fillets on some scrap tube and post up some photos.
Actually another question I have which is relevant here is how critical is it to build an internal fillet, or is simply getting good penetration across the butt/mitre wall adequate (assuming in both scenarios there's a good buildip of brass on the outside of the join)?