I use an immersion water heater to warm up the water tub that I use to soak off brazing flux. This is my third version, the previous two both crapped out. If this is what you are talking about I suggest you only have it plugged in when under water or the coil will overheat and fail.



However I don't think you're talking about this type of heater. I am uneducated about induction heating, only know of the stove top version. That the bike frame has so many curved surfaces I wonder about how evenly induction would heat it up (sauce pans have a nice flat and large bottom). The varying thicknesses of the tubes, lugs and such might also prove challenging to get evenly hot. Then there's the aspect of the filler/braze being able to be heated by other that the joint's warmth. Does induction work on bronze or silver? Getting the filler to melt by only the joint's heat might mean having the joint really hot (as in too much). If induction heating acts like a convection stove top burner there's a time delay between "adjusting" the temp and having the work piece change its temp. I would think this delay would cause frustration for the brazer and any overheating would last longer as the "system" time to cool a bit is slow. (With a torch one only needs to flick the flame off the joint and the cooling is rapid, flick back and temp control is quick and easy). The size of an induction device might be significant, as well as the cost as Francis suggested.

I think the closest the industry gets is electric resistance heating, as in welding. But the heat is very localized and the tig torch, like the OA flame, can heat and cool rapidly with much control. There's a thread on another forum currently about Tig torch brazing and the consensus is that the braze/filler doesn't wet out on the steel to the same degree as with a flame. There are questions about resulting joint strength.

But many smart people have been blinded by tradition and wanting to continue techniques they already have mastered so I say have a go and report back. When you do post a follow up consider doing so in this forum's framebuilding sub forum, not the general mechanics one. Andy