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Thread: 2.5 mm Cooksons setting

  1. #1
    Join Date
    Aug 2013
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    Default 2.5 mm Cooksons setting

    Hi,
    I need an advice with setting.
    I bought this setting: http://www.cooksongold.com/Settings/...prcode-NN1-112
    I wanted it for 2.5 mm black diamond. But the setting is little bit larger (2.6-2.7 mm) and when I place the stone inside, I can see a tiny rim of metal. That means setting is too big for 2.5mm stone. But i think it is too small for 3mm.
    I am not experienced with this type of setting and I am quite confused. According to description it should be for 5pts (diamond?).

  2. #2
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    Jul 2009
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    Romsey
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    Default

    According to my charts, 5pt is 2.4mm but never mind. When you say you can see a tiny rim of metal, do you mean the gallery? With commercial settings I usually expect to remove metal from the gallery to get the stone to sit low enough - it's more of a problem with deep-bellied stones that don't conform to the ideal cut for that shape though.

  3. #3
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    Aug 2013
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    Yes, the gallery. I probably can remove some metal and it needs stone-setting burr anyway, but I am worried that I ruin it.
    Thanks.

  4. #4
    Join Date
    Feb 2014
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    Manchester
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    Default

    Just to make sure, are you saying that the 2.5mm stone already sits between the prongs all the way down on to the gallery? If it does then it sounds as if you won't have much leeway to remove material.
    BTW, what's your main worry about using a setting burr specifically? Are you worried that it's the setting burr that will ruin the job, or that just removing material some other way may ruin it? Whatever happens, you'll have to create a seat for the stone, so material will have to be removed.
    BTW 2, I've learned to use Cooksons measurements as only a rough guide to stone size, not a definitive statement.

  5. #5
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    Feb 2013
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    If there is a gap between stone & claws don`t bother trying to set it.
    If stone is touching claws you might get away with it but don`t cut a bearing into the claw..also burnish the outside edge of the gallery at an angle.

    Ideally the stone should not quite be able to sit flat in the setting.

  6. #6
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    Aug 2013
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    Aurarius, no, not all the way down. I need to use 2.5mm burr or cut the bearing into the prongs (or both).
    But then it will be too wide, because diameter of the gallery is bigger then the stone (something between 2.6 and 2.7 mm, stone is 2.54 or something like that).
    The prongs are not fully outside of the gallery circle, they are partially in it. So the inner distance between two opposite prongs is smaller then the outer diameter of gallery. I don't know if it makes sense.
    Burnishing outside of the gallery could help.

  7. #7
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    Even I'm getting confused now
    Don't over complicate.
    Clean up & burnish the outside & top of bezel nice & bright & minimize what you can see.
    Don't drill anything for the sake of it just because your "supposed to" & only as much as needed if any.

  8. #8
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    It is possible to bend the prongs out a little too, but if you do decide to use a setting burr, please avoid one of those hairy Dremels.

    You can mount your burr in a universal handle, such as Cookson 999AZM, oil it a little and turn it by hand. This will give you much more positive control. Dennis.

  9. #9
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    Feb 2013
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    Finland
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    I`ve a job here today (in fact 3 of them), with too small stones.
    So..I push the claw over as it is, rather than cut a bearing in the claw which would make the metal even further away & make things worse.
    Click image for larger version. 

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  10. #10
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    Feb 2014
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    That's very interesting, Chris. I didn't know it was accepted practice, but clearly if the stones you've been asked to set are undersized for the setting you've not much choice. Do you have to do any compensatory filing on the outer edge of the prongs in order to make them more willing to bend in the place you want them to bend, or would this depend on initial prong thickness?

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