Imagine a flat copper donut. You want to solder a flat silver donut hole
into the center. You have a fairly good fit, you flux, you put your solder
chips around the seam, you torch it. The gosh darn thing simply will not
bridge the seam at cerain areas and you eventually scorch the donut hole into
unwanted reticulation. How can I marry the hole to the donut perfectly?
It appears the issue is that the copper and silver expand at different
rates and the outer copper one (because of its shape) expands leaving your
You could try having a slighlty bigger silver disc than will fit the hole,
when the copper expands it will drop in the hole and then solder it. How
much bigger? Some, not too much. (You could of course heat the donut and
measure how much bigger the hole is when it is hot)
you could try pumping most of heat into the silver disc so it expands first
(postential soldering problems with this route-ideal is everything going up
Whatever you do use a ton of white paste flux. You need a long working time
with this one and that flux will give you enough. If your flux begins to
turn green put some more flux on. If the flux is brown you will have to
start over. Do not pickle as a pickled finish interferes with effective
solder flow (seams need to be scraped or cleaned prior to soldering) You
can’t have too much fluw when working with copper (and sterling for that
matter), golds are fine with a thinner flux like Batterns or Pripps.
Tell us what worked-should hear some more from the list on this one.
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