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Thread: Sizing of cast rings?

  1. #21
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    Oh, yes it was very informational, thank you!

    Now I at least know where to start when sizing and won't end up a size too small just because I wanted to be on the safe side (which was actually the wrong side)!

    I think I will still cast it in silver first just to confirm the sizing and feel of the rings, even if it means it will be a tad more expensive.

    Again thank you for going through the trouble of making, measuring and documenting the procedure, it was really appreciated!

    /Andreas

  2. #22
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    Oh, by the way, the plain rings are simple enough to make a bit bigger, but how about rings with heads/prongs?
    Do you make them to size and then resize them with a factor, or you add a bit of width to everything, like gem sizes, prong thickness, etc to adjust for shrinkage?

    /Andreas

  3. #23
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    I make with the same allowance as the simple band (half a size), Andreas, but I do make sure that there is enough metal in the band to allow for adjustment through filing the inside of the ring or rolling the back, ensuring that the integrity of the setting is maintained.

  4. #24
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    Thought of a new question (naturally)

    What kind of abrasive do you start with when cleaning the castings up?
    All the way from white silicone (very coarse grit), or do you start with something a bit less agressive?

    Using a micromotor, so I will probably go with mini-polishers of silicone or 3m radial wheels.

    /Andreas

  5. #25
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    There are endless ways to skin this rabbit Andreas, but for me the principle concern would be to preserve the court profile.
    Wheels and flat things will most likely ruin the shape of the shank.
    So, using your motor with as light a touch as possible and not staying still in one place, I would start with these:

    http://www.cooksongold.com/Jewellery...prcode-999-ACR

    and finish with these: http://www.cooksongold.com/category_...y=Radial+disks going through all the colours starting with yellow.

    By the time you reach green, a final shine if necessary, could be effected by a polishing cloth. Dennis

  6. #26
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    Thank you!

    I already got the 3m discs and they are great!
    I also have white and orange Luxi for final buffing and a good polishing cloth for all the nasty fingerprints.

    Just some scotchbrite wheels left then!

    /Andreas

  7. #27
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    By the way, how about tossing it into the rotary tumbler for some added work hardening and polishing?

    I know I will still have to clean it up and do a bit of extra polishing and buffing afterwards, just curious to what it does to casted pieces.
    Theoretically it would harden them I guess which would be good provided they do not need resizing on a mandrel...

    /Andreas

  8. #28
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    The consensus is that tumbling has a minimal effect on work hardening and then only on the surface. You also have the problem of needle marks.

    To harden a cast ring without stretching or hammering, which might crack it, you can put it into a kiln at a set lowish temperature for some hours. Unfortunately I don't have the data, which is specific for each alloy. Dennis.

  9. #29
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    Aug 2013
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    Halmstad, Sweden, Sweden
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    Default Results!

    I thought I'd pop in and tell the results of my first casting endeavor.

    Firstly, I asked the casters how to size the ring and was told that I should make the CAD drawing to size, so I did, but added a tiny bit extra thickness to account for cleanup.
    Supposedly their printing software accounted for metal shrinkage.
    I was quite nervous when I got the rings and surely enough, one of them was miscast (Was slightly oval and about 17.4 mm in inside diameter instead of 17). I sent it back and they replaced it though, so credit for that, but it would have saved me postage and 1 weeks of waiting if they had taken ten seconds of measuring it in quality control.

    Rings looked quite dull grey when I got them, but were fairly smooth, not too bad artifacts from printing, I guess the Solidscape printer did a good job.

    I proceeded with filing the remains of the sprue off the ring with grade 0, 2 and 4 files until it was smooth then headed over to my micromotor for polishing (I might want to get a real polishing motor the next time, it would probably go faster since I can just move the ring with two hands instead of coordinate ring and micromotor)
    For polishing I smoothed the surface with silicon cylinders. I tried scotchbrite wheels, but didn't like it littering my workbench with dust, and I might have gotten a too fine brush as well.
    I kind of expected it to be soft so I started gentle with the silicone. Found out quite soon that the palladium actually was quite hard, not at all like the sterling I had been polishing earlier so it took a lot more effort to get it nice and smooth.
    Kind of guess that I need some more experience in polishing as well. I did work my way through white, black, blue and pink though.
    After the surface was smooth I sanded the sides with wet sanding paper (400, 800 and 1200 grit), as well as smoothed them out with the silicon cylinders.
    Then I used the mini 3m radial discs on the entire ring to ensure that there were no irregularities and the edges was smooth. Up from 400 grit to polish (Blue, Pink, Peach and Light Green).
    Lastly used final buffing with Lux white and orange.

    A new experience, and I guess you get better at it the more you do it. All in all I spent a better part of 10-12 hours of cleaning two rings, but hey, it is the first time and I had to do a bit of re-polishing due to scratches, plus that I was a bit too careful with my ring in the beginning and had some artifacts left from the casting and I needed to polish it all over again.

    Will show a couple of images (just of my ring though, since my girlfriend is lurking here sometimes and I don't want her to see her ring just yet).

    Click image for larger version. 

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    Ring from caster

    Click image for larger version. 

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    Finished ring

    /Andreas

  10. #30
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    That's turned out nice Andreas, and you've got a good shine on it too.

    Quick question though, why did you feel the need to have this ring cast when ( judging by the design of it ) you could have quite easily formed it yourself from the wire?

    Nick


    Sent from my iPad using Tapatalk

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