Using solders having different melting points can be a useful technique even if, like me, you don't have a temperature-controlled iron. However, in my experience higher melting point solders have less good wetting properties than lower, and on very small assemblies I have difficulty making a satisfactory joint with high melting point solder. Perhaps I've been unlucky with my choice of such solder.
I do get good results from Carr's 183 tin/lead solder when assembling pre-tinned strips of nickel silver into T-shaped lamp irons. To solder such assemblies in place I use the technique illustrated below, again using 183 solder to secure the assembly to the tender or bunker backplate.
Soldering lamp irons.jpg
The assembled lamp iron needs to be freed of any excess solder that might cause the iron to become attached to the tweezers, although the risk of this is reduced by the use of stainless steel tweezers, to which the solder is more reluctant to adhere. The benefits of this technique are:
(1) the tweezers are holding the lamp iron's two components in correct alignment as you solder – even if the solder joint between them liquefies whilst you are attaching the assembly to the tank/bunker, they will retain that correct alignment when the joint cools again
(2) the tweezers act as a heat shunt, reducing the likelihood of the lamp iron's two components separating in the first place.
I prefer nickel silver to brass for the strip from which I make lamp irons – stiffer, stronger, lower rate of heat transfer. I make suitable strips of n/s by cutting it with a skrawker from .005” shim.
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