Australian Facetors' Guild Limited

Transposing angles on odd shapes

  • 12 Feb 2020 6:15 PM
    Message # 8741998
    Deleted user

    Hi All,

    Perhaps a noob question, but I get a bit lost with the whole angle transposition once there are numerous angles involved. For example I have a pear shape design with pavilion angles ranging from 39.49 to 48.5 for an R.I. of 1.54 & wish to cut it in Zircon with R.I. 1.94. Is it going to give a good result just using the quick & dirty method of scaling the crown & pavilion individually in Gemcad? 


  • 13 Feb 2020 7:35 AM
    Reply # 8743593 on 8741998

    In short, yes.  Hans E has successfully used the ray trace function in Gemcad to show him the effect of angle changes and then optimised an oval adjusting the crown and pavillion angles in gemcad.  I wasn't able to appreciably improve the design using Gemray.  He's a retired engineer and much better at geometry than me.

    I just use Gemray or Gem Cut Studio to optimise each design before I cut it.  They are quicker and easier.

  • 17 Feb 2020 7:58 PM
    Reply # 8751547 on 8741998
    Deleted user

    Thanks Gordon, I have just started using Gemcad & Gemray & have been startled at the results when optimising angles given to me by someone who has cut Sapphire for many years. I was also amazed at the improvement when rotating the crown facets on a round brilliant to the opposing index. Now to cut some & try to verify my newfound knowledge!

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