Bought a load of shit tubes and made numerous terrible bikes for myself and friends. I never paid attention to anything at school so had very little hope that I'd learn anything on a course ;)
Great, whats easiest to start practicing, lugs or fillets?
And as mentioned in the other thread. For home novice practice, a Mapp torch is ok for silver brazing but not brass, and silver is a bit harder to get right, that correct?
What would you suggest to cheaply give it a bash? Not bothered with jigs and angles, just want to actually join two chunks of metal together
Some sort of torch, gas, brazing rod, flux. That it? (in materials, exc safety equipment)
Lugs can both pull in more brass/solder and sink more heat, making them harder/slower/expensiver to unpick for mistakes or practice.
Using lugs is easier since you ideally have the tube diameters the lugs were designed for, just need to get the lengths right. You are restricted in terms of both overall geometry and detail geometry, for clearances.
Filleting tubes gives you a lot of freedom, but you'll need to make sure the curves each end are aligned properly. Assuming the ends are correct though, if you get your jig setup wrong (e.g downtube-seattube angle slightly off could result in your toptube and headtube not meeting) you can still separate the tubes and redo earlier joints (assuming you don't overheat a fancy tube and ruin the heat treatment).
Lugs if you want to build a bike, as you can easily build a frame without a jig, brazing you will at least need some sort of flat surface, theoretical at least (see what @s.walrus is doing in this regard.
Lugs are easier, not least because they hold everything in place while you wave a torch around while poking yourself in the face with some welding rod. However, due to the amount of metal you need a torch with some serious ooomph. It's not so much the temperature of the flame, as the total amount of heat it can chuck out.
Fillets are harder to do, particularly with silver. The hard thing about silver is that when it melts its very runny, almost like water. Overheat a brass fillet and it'll get a bit saggy. Overheat a silver fillet and you'll end up with a little puddle of silver on the floor. You also need to be much more careful with cleanliness and contamination with silver. If you cook the flux then it's game over, start again - brass is far more resilient to a bit of overheating.
The downside with brass is again the extra heat required. You can add little braze-ons using silver with nothing more sophisticated than a standard plumber's blowtorch. Doing lugged joints with brass is going to require oxy-propane or oxy-acetylene like @coldharbour says.
If you just want to stick some stuff together, I'd suggest just getting a blowtorch and a small quantity of silver and flux, something like a bit of Fillet Pro from Ceeway and some System 48 flux. You won't be able to build a frame using it, but it'll be good practice anyway with little capital outlay.
Then once you've upgraded to oxy kit, get some practice tubes and lugs from Ceeway and do a load of them. Then move onto your first lugged frame and you're away...
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