On Saturday, November 10, 2012 1:07:00 PM UTC-8, Paul K. Dickman wrote:

I am looking to put together a purpose built soldering machine

I have a 6"x8" piece of 16g polished brass sheet and I need to soft solder
an 8" brass piano hinge to the polished side.

Brass (because of zinc content) solders best with some acid flux. Start
by cleaning the section (hot blade? wire brush?), then wipe with flux and
tin by running an iron over the area.

An iron applying local heat is better than trying for a large heated block
in total contact, and if both surfaces are tinned it doesn't need any long
application of heat to complete the join.