Originally Posted by
BoozyMcliverRot
Lots of good info here guys. Thank you. I've watched a couple videos of Jodi over at welding tips and tricks and he used silicone bronze. Is there a specific rod I should use? 1/16 tungsten or 3/32? What type of tungsten do you recommend?
I have experience brazing heat exchangers that I did for about a year but that was with flame and not electrode.
Silicon bronze is the stuff you want. Make sure it's a TIG rod and not one meant for a gas torch. If it's the latter it will fry and spit and try to poison you with fumes.
I use 1/16 tungsten but it's not critical. Get the 1/16 bronze rod (but for welding use a 1mm rod on most joints). I use 2% lanthanated for everything as per Jody's advice (I have an inverter machine).
Start heating the joint but don't wait for it to puddle like you would for welding, or only just. Just enough heat is when the puddle is making a nice profile at the edges rather than being convex on top. But if it is convex it's easy to just run the torch over it again to zap it in.
The idea is not to mix too much steel in with the braze. You shouldn't be melting the steel.
You can turn the gas up a bit if you like but it will always look a bit grimy when you're done. A very little wire brushing and/or scotchbrite will quickly bring back the bling.
The bits that will kick your ass are behind the seat stays and between where the chainstays join the BB shell. You will need to wrap things in foil and be creative to keep the gas where you need it. The other spot to be aware of is where the DT meets the ST. Both tubes are thin at that point so take care. Everything else on the bike is thin to thick. The top of the ST and the HT usually are thicker than the main tubes and the BB shell is really thick. So direct the heat accordingly, although this applies more to welding.
Have fun and post pictures!