I have managed to silver solder (45% silver) using a mapp turbo torch.
I have also tried a Sievert and it was ok for very small items but
my torch heads were on the small side.

A good reference is that you have to get the part to red color. If your
torch can't do that in a reasonable time, you need more heat.

contrary to what someone else said, silver solder will fill small gaps
but optimum gap is just a couple thousands of an inch. It depends
greatly on how much heat you have. Very hot and its very thin. cool it
down to just above melting and you can create fillets too.

chuck