antigoon
Rough_Rock
- Joined
- Mar 18, 2004
- Messages
- 30
It seems that most of the diamonds I've seen lately have had their crown and pavilion angles right along the "ideal cut cliff", where the diamond's HCA score can fall from 1 to 3 with the slightest variation in crown and pavilion angles.
/idealbb/files/t563.gif
[/p]Table : 56
Crown Angle : 35.1 (35.0-35.3)
Pavillion Angle: 40.9 (40.8-41)
[/p]
If I plug in the average angle values (35.1, 40.9), I get a respectable HCA score of 2. If I plug in the minimum values (35.0, 40., I get 1.4. But if I plug in the maxima (35.3, 41), I get an HCA score of 3.
(Again, I understand that the HCA is a rejection tool, not a selection tool. My question #1 below is about whether I should reject diamonds that have a “worst-case” HCA >2.)
/idealbb/files/t56.gif
I’ve got three questions:
- Am I justified to be worried about any diamond whose proportions “fall off the cliff” like this?
- There is a margin of error in the Sarin and other measuring machines. Unfortunately, this margin is not listed on the reports I’ve seen to date. (This is too bad, because the more expensive Sarin machines are more accurate than the less expensive ones, but if I don’t know what kind of machine it is, I have to assume it’s the less accurate one.) So should I take an additional ±0.1 degree to account for possible measurement error when measuring HCA, “just to be safe”?
- Why are there so many diamonds that are right on the edge of the cliff? Is there something inherent in the geometry that makes it easier to cut a diamond that way?
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