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Thread: Problems with rolling 9ct gold

  1. #1
    Join Date
    Jun 2017
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    34

    Default Problems with rolling 9ct gold

    hi, I've been sandcasting gold rings for a while but thought I'd try making some bangles then maybe have a go at making a curb chain.
    I've recently picked up a new rolling mill and Researched the hell out of which way to go about making 9ct yellow gold wire.
    The problem I'm getting is the gold starts to get small cracks after rolling for a while (whilst annealing in between). And I can even snap the gold like a matchstick.
    I've seen so many different ways online of the full process. Which is the best way? Or where am I going wrong?
    I'll list equipment I'm using then process...
    Small kiln with 4oz graphite crusible
    Wire reversable ingot
    Basic rolling mill (unknown make/cost 180)
    9ct scrap yellow gold. (Already melted down 2 times)

    Melt in crusible adding a small amount of borax toward the end
    Heat ingot slightly
    Pour
    Run through the mill as I've read everyone does, closing down slightly each time
    After around anneal until red, leave till red goes away then quench
    Then mill again.

    I have read that hammering down after pour can help but I haven't tried this yet.
    Will try this today.

  2. #2
    Join Date
    Mar 2016
    Location
    Vancouver, Canada
    Posts
    19

    Default

    I'm definitely no expert, but do you need to quench?

    When knife making, quenching hardens the metal and makes it more brittle and prone to snapping. And only done just before finishing stages, after shaping has been completed. It's prior to quench and post-heating that the metal is soft and best for reworking. I don't know if this all translates over to jewelry though, as the properties of gold are much different than steel.

    I hope this helps but maybe best leave this to someone more experienced than me!

  3. #3
    Join Date
    Jun 2017
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    34

    Default

    Thanks for the reply, just about every video I've watched it's quenched but I'll try still that.
    It's a long process of trial and error but I'll get there

  4. #4
    Join Date
    Dec 2009
    Location
    Central London
    Posts
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    Default

    And while the wire is fat, reduce the gap more slowly and anneal after two passes.

    One of the problems with annealing wire is that if the flame is too fierce and not moved around a lot some sections will become overheated and too brittle to work. Anneal in a darkened corner and never heat more than dull red, as evenly as possible.

    If your annealing is successful, the wire will feel soft to slight manipulation by hand. Obviously making wire in a mill is not entirely successful and you next need to think about draw plates for the final passes.

    Unfortunately, the heat treatment of ferrous metals is completely different and almost the direct opposite. Dennis.
    Last edited by Dennis; 15-04-2018 at 01:37 PM.

  5. #5
    Join Date
    Jun 2017
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    34

    Default

    Thanks Dennis. Yes I do have a draw plate set up in a vice ready.
    Maybe it's down to the annealling then.
    I'll try annealling it more often.
    Just to check the way I'm doing it is right...
    I heat the metal with the tip of the flame at one end until red then move along it making the rest red as I go. So not moving the flame side to side.
    Then leave it till the red has gone then 5 seconds or so then quench and roll

  6. #6
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    Central London
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    As said above, the wire is easily overheated in patches and will then break. The point of the flame outside the blue cone is the hottest part, so pull the flame back a little and move it from side to side, to avoid lingering in one place.

    A darkened area allows you to check that the metal only ever goes to dull red and that you have done the whole length evenly. Dennis.

  7. #7
    Join Date
    Sep 2014
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    2,068

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    It may be better to anneal the wire in the kiln to get a more even temperature across it?
    Its definitely the annealing that is the problem.
    This table may be useful although it doesn't give the time needed:
    http://www.nancylthamilton.com/wp-co...for-Metals.pdf
    Also this video shows 14k gold being annealed in a kiln throughout the drawing process:
    https://www.youtube.com/watch?v=WlIuO0aKfqk

  8. #8
    Join Date
    Jun 2017
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    There seems to be a lot more to it than I thought.
    I've been sandcasting gold rings with scrap for a couple of years now and never really come across many issues.
    I've just read that it's advised to add new gold to the melt as scrap gold can crack etc when milling for a variety of reasons.
    Which in turn will make my hobbie very expensive.
    My kiln is very basic. It only holds a 4oz crusible and has no temp indicator.

  9. #9
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    Sep 2014
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    Ah ok, just thought it might be easier but obviously won't work with that kiln.
    In that case just follow Dennis' advice above and be careful to heat it evenly.
    I did read that you should hold at the dull red glow for 30 seconds so I always do that with mine, any less and it doesn't always anneal properly.

  10. #10
    Join Date
    Aug 2017
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    Default

    Quote Originally Posted by Simmo View Post
    ..
    I've just read that it's advised to add new gold to the melt as scrap gold can crack etc when milling for a variety of reasons.
    Which in turn will make my hobbie very expensive.

    I am very far from an expert, but I believe this is only recommended if you don't know the source and/or quality of the scrap you are using, or, you are melting down scrap jewellery that has been soldered in places. The experts say that it is the impurities like solder in your scrap that causes the metal to become brittle and crack when cold working. This is why they advise adding pure gold or silver (depending on the alloy you are working with) to your scrap.

    But, if like me, you make your own alloy, and all your scrap comes from the same stock, and none of it has any impurities like solder in it, then I cannot see any logical reason to constantly add new silver or gold to it. There is nothing in the process that can alter the properties of the alloy, unless I am missing something(?).

    This isn't just pure theory, I make my own sheet from my own stock of alloy, and my scrap has been melted down and rolled into sheet countless times without ever adding any new silver. No cracking or brittle problems yet.

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