I've been trying to solder a U-shaped piece of wire to the top of a
dapped 1930 Canadian 25-cent coin, which is 80% silver. I don't know
what metals represent the remaining 20%. I'm using hard silver sheet
solder, and can't get the solder to flow.
I've tried soldering the pieces lying flat on a charcoal block and a
honeycomb board, from otherneath on a tripod screen, and with the
coin held vertically in a third hand, and have tried Battern's liquid
flux and a paste flux. I've cleaned the pieces thoroughly with pickle
and steel wool, so I don't think cleanliness is the issue. And I
smoothed the top rim of the coin to remove the rim grooves.
I think the problem is positioning, or that my wire ends don't
flawlessly fit the coin rim surface, or something to do with the
metal content of the coin. Once I (accidentally) got the metals red
hot, but the solder remained solid.
What is the best way to hold/position the dapped coin and bail wire?
Where is best to place the solder chips? And how can I get the wire
ends to more exactly fit the curved coin rim? I tried hand-filing and
using a flex shaft grinding wheel, but the fit was not perfect.
Any advice you can provide will be much appreciated.
I solder findings to domes of silver and coins a lot. Why the U
shape? I use small jumprings to solder to coins and domes. Use a
round file to make a curve in the edge of the dome/coin for the
jumpring. When the jumpring fits into the curve, I solder with,
depends on size, either solder paste or solder. The trick is to get
the solder to NOT 'run up' the jumpring. Heat from the coin side. Use
lots of flux. If not sure of the metals other than the silver
content, clean of flux with hot water. Do not put in pickle.
Australian older six pence coins that are sterling silver do not
react well in pickle.