Don't be convinced that Silver soldering is not going to work too
quickly. Take a look at the Hardy and Handy meb site. Hard silver
solder can have a strength of about 100,000 psi in a lap joint. Silver
solder is ( or at least was the last I knew ) permitted to use on US
Navy submarines for thru hull fittings. They don't like it because it
is hard to verify the work with NDT. But it is plenty strong.

A propane torch can be used for hard silver soldering, but you have to
be ingenious in keeping the heat where it is needed. You would not be
able to do it with propane in the open air.


Dan