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Thread: Thermal Expansion

  1. #1
    Join Date
    Jan 2017
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    Default Thermal Expansion

    Hi there,

    A couple of years back I made some wedding rings in 18ct gold. At the time I didn't realise that the the guy worked a lot with his hands - mechanics etc... (in hindsight would have recommended different metal - sigh - silly me)
    So just a few backs the guys ring split. My thoughts were that I could repair, cut out split area and then solder onto thicker silver to strengthen and solder and resize. No problems soldering the gold onto the silver (so now completely sealed) but when trying to solder the seams together they move away from one another every time. After a bit of research I think this is probably due to the different rates of thermal expansion in the metal? I have tried binding with wire but not tight enough - but don't want to damage ring. I have read that I could have made two rings and fitted one inside the other but of course now I have soldered top to bottom that it seems a bit past that. Has anyone got any tips that might help with solving this? I am at a bit of a loss... Or is it a lost cause? (oh dear).

    Any thoughts would be appreciated.
    Thank you.
    Laurarara

  2. #2
    Join Date
    Dec 2009
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    Default

    Hi, Laura. this is a time when I can't really visualise where you have put the silver (or why silver?). It is unlikely that you will be able to undo it, so without a photograph to contradict me, I would say scrap the ring and make a new one.

    18 ct gold is much stronger and harder wearing than silver, but if he is a manual worker, a titanium or stainless steel ring might solve your problem. Dennis.

  3. #3
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    Jan 2017
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    Default

    Hi Dennis,
    Thanks for the reply. The couple wanted the original ring repaired. It is 18ct white gold. I have put 0.9mm silver what would be the inside of the ring when soldered to strengthen, also thought the contrast would work well.. I've done the same with silver and copper but of course didn't have this issue. I'm afraid I don't work or have the capacity to work with steel or titanium so that's out for me I am afraid (plus the type of texturing on the ring which I don't think would be possible with titanium but that's kinda a side issue.)
    Any other thoughts?
    thanks again

  4. #4
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    Well then I suggest that you have one more go, using stronger binding wire as follows:

    Get some 0.45mm stainless steel binding wire such as Cookson 998 019B. Double a piece up and twist lightly so that it is two ply.

    Anneal by heating to dull red and air cool. Tie it across the ring, with two adjustment loops, one on each side. You will find that this can be tightened without breaking so easily.

    Also, heat the ring at some point remote from the join, which will tend to keep it together more. Hope this works for you. Dennis.

  5. #5
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    Jan 2017
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    Default

    Thanks so much Dennis. Really appreciated. Will give it a try and let you know! x

  6. #6
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    Sep 2014
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    Default

    I still don't understand how silver will be a good idea when its softer than the gold?
    Titanium does work great as a wedding ring for men who work hard with their hands, my husbands is barely marked or worn after him wearing it for 11 years now.

  7. #7
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    Jan 2017
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    Default

    Hey enigma,
    Well I don't know if you read above but repair is what the person wanted, so titanium yes is great and hard wearing, but again not what the person wanted. Next time I will know better!
    It's thicker than the gold, put on inside to strengthen frame of the ring.
    Thanks

  8. #8
    Join Date
    Sep 2014
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    Hi Laura

    Yes I get that but why would you repair an 18 ct gold ring with silver?
    I have a feeling you may have an issue with hallmarking now too?

  9. #9
    Join Date
    Jan 2017
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    Default

    Dennis thanks so much for your suggestion although I cant seem to get the wire tight enough even with adjustment loops... Hmmmm... I think working against the laws of physics may be a little optimistic... Ah live and learn.
    Any other last advice or thoughts from anyone? Or RIP ring?

    Just found this but might have to make my own T-pins:
    "I now combine 18 k or 22k with argentium in all my work. The differences in expansion of the metals is what is causing this. I set the ring flat on a soft charcoal block and use T-pins stuck into"

    Would love to hear any success stories!

    Also this which is just useful info just found I think pre trying this kinda thing... and if I hadn't have soldered first flat I probably would have tried this.

    "With the new band, to avoid the differing rates of expansion, I
    made two flat bands and fitted one inside the other. I still had
    a problem with the different expansion rates. The seam was
    difficult to solder seamlessly. I feel for the next guy thst
    tries to size this ring. I won't be doing it."

  10. #10
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    Jan 2017
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    Default

    Ooo Just found this:


    Probably more like what you meant Dennis? I visualized it differently stretching across rather than around.

    Think the ring is now held tightly... gonna give it one last go.

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