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Thread: Polishing to a mirror shine - problem!

  1. #21
    Join Date
    Apr 2011
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    103

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    Just as a note - next time I bend a flat piece of sheet into a ring - is there anyway of avoiding the cupping? I use a tapered ring mandrel.

  2. #22
    Join Date
    Dec 2009
    Location
    Central London
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    7,600

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    Well, I have made lots of rings over a long period and never heard of this problem. But then I have never taken files and buff sticks to the surfaces either.

    In another post today, I wrote this:

    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.

    You might try this method in your case too. Dennis.

  3. #23
    Join Date
    Apr 2011
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    103

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    Thanks Dennis - the links do not work presently (think the site is being worked on) but I realise what the radial disks are - must invest in these!

  4. #24
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    Apr 2011
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    103

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    On a future note - is there any way of preventing the cupping?

  5. #25
    Join Date
    Jul 2009
    Location
    Cornwall
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    3,168

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    If I understand you correctly, the tapering of the ring can be rectified if you turn the ring around and hammer it on the other edge.

  6. #26
    Join Date
    Aug 2012
    Location
    Oxon
    Posts
    394

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    Yes, but on a micro (macro?) level, it will always be >< shaped, it has to be if you are using a taper to form it.
    you end up with two opposing very very slight tapers, the outside edges (leading edges) are a very slightly larger diameter than the centre diameter. The wider the ring, the more pronounced effect.
    I think it is this micro, virtually unnoticeable dip which is causing the problem. I could easily be wrong though.
    A few curving wipes with a fine file around the circumference takes the outside diameter down to the smaller centre measurement.

  7. #27
    Join Date
    Feb 2011
    Location
    Scotland
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    The ring should never be shaped if you do as Carole says and on every full working of the ring you take it off the mandrel and turn it round and put it back on and work that side. As long as you keep on turning the ring round it should be flat. Once finished on the mandrel you just go round the ring with your hand file wrapped in emery paper to take down any possible unevenness

  8. #28
    Join Date
    Apr 2011
    Posts
    103

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    Just an update: got back to sorting the ring today. Went round it with my file and the a mixture of hand and Foredom polishing and it has come up a treat. Have now invested in some radial discs too.

    Thanks for the other advice too - I did turn it but probably not a regularly as I should!

    Many thanks - many lessons learnt!

  9. #29
    Join Date
    Feb 2011
    Location
    Scotland
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    2,551

  10. #30
    Join Date
    Apr 2011
    Posts
    103

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    Yes - thank you all who helped

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