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@Jingle_Jangle
Did a little bit of practise brazing last weekend.
Brazing is different from welding. With welding you actually melt two pieces of metal so that they join together. You might use a filler rod to strengthen the joint, but the key point is you heat the metal to melting point.
With brazing, the joint is made secure by a filler. A filler is a metal that has a melting point which is lower than the metal to be joined - you heat the filler until it becomes liquid, and then introduce that liquid to the surfaces to be joined.
Fillers used in bicycle making are usually either Silver or Brass. Most of the 'how to' manuals recommend Silver as a filler. I think this is primarily because Silver has a lower melting point than Brass, and can therefore be used with MAPP Gas, which is available from DIY stores - you can even get it in B&Q.
Which ever filler rod you choose, the principles are basically the same.
With fillet brazing two mated surfaces a joined together by building up a 'fillet' of brazing material. To achieve a decent finish using this technique requires a great deal of skill, and is not recommended for the novice builder.
My build will utilise a 'lugged' construction. With this method, a sleeve or lug is placed over the two tubes to be joined. The very fine gap between the lug and the tubes is then filled with either silver or brass which has been melted using the torch. The molten filler is persuaded into the gap by a combination of gravity, capillary action and the use of heat.
That's the theory anyway - in practise, it's a bugger to get the hang of. Here are the results of last weeks attempt:
Not pretty in any way.
I think I made a few schoolboy errors. In particular, I think I heated up the tube and lug too much. This meant that the brass went all over the place, rather than where it was supposed to go. I also tried to rush it, which is something you can't really do.
Hopefully, I will be able to have another practise tomorrow - until I master this skill, I won't be going any further.