Another call out to say thanks for all the combined wisdom on this site!
I spent the weekend cutting some synthetic corundum.. I've done it before, and experi need what I though was directional hardness; but it was a minor issue... But not this weekend! This time is was a major issue!
I only sort of figured it out today, but couldn't come up with a reason why is was so much more an issue with this design (cutting 4 pieces with the same design) versus when I'd cut other designs...
Well this one is (almost) square, and to align for maximum yield, of course I line up two of the sides with the long axis of the boule. The difference in hardness between the long axis sides and across the boule was so enormous I couldn't believe it. I thought I had gummed up a lap, destroyed it, or any number of other things I tried to explain it; but then I'd shift to another facet and it would be fine - I got a little frustrated. The stone today though, I paid attention to which were the hard facets and which were not... and then did a search on GO.
This is cheaper, flame fusion material, where I aligned it in (apparently) exactly the wrong orientation. I will orient large facets on this material in a different direction from now on.
Joined: Mon Aug 20, 2012 11:32 pm Posts: 1747 Location: Florida, United States
I see you have discovered the issues with directional hardness in corundum. While that phenomena is not nearly as pronounced as it is with diamond, it can be annoying. After preforming on the 32 micron sintered lap, I recommend using your 12 micron sintered lap to facet and try different dop orientations and if not good, reverse the direction of the motor and try different dop orientations again. Prepolish with 2-4 micron on the BATT.
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