Does the cut adviser work without Pav. & Cr. angles?

[Leanne]

Hi. Does the HC Cut Adviser only work well if you have the pavilion & crown angles? I entered my diamond''s table, 55%, & pavilion depth, 63.1% and left the fields alone for the angles. It came back that my stone was OK. By doing this, does it give me some idea if my stone''s cut is allright?

 

[Garry H (Cut Nut)]

Sorry, that is a big no!!

 

[Mara]

If I am not mistaken, when you load the Cut Advisor into your browser, the fields come pre-filled with data that constitutes one possibility of an 'ideal' stone's dimensions. So by changing the table and depth to your own stone's #'s, but leaving the crown and pav angle the way it came pre-filled, you are telling the HCA that your diamond has those angles and asking it to compute the data based on those angles and your table & depth. That is not accurate at all, that is ONE possibility out of many more.

For example, if I put in my table and depth and left the pav and crown angles the same, it would be an ENTIRELY different stone. In fact my crown angle is almost 4 degrees difference from that 34.5 that is pre-filled. My crown angle *could be* 34.3, 34.1, 33.9, 33.7 etc..the list goes on. Any amount of change to the crown or pav angles will modify the score. If it comes pre-filled with 34.5, but my crown angle is 29.9, you can see how assuming that your stone may have similar angles to what the HCA comes with will be very incorrect and misleading.

You need all 4 fields, culet is not always required as most round brilliants have little to no culet which will not modify the HCA score..but if the culet was 'medium' or 'large' then you'd need to plug that # in as well to get a more accurate score.

Even if you have all 4 fields...the HCA assumes that we are talking a very symmetrical stone with very good polish. So if your symmetry is 'good' vs say an 'excellent', your stone will perform differently than the HCA says (and it probably will anyway if even just a tad)...HCA is an estimation. Also, if your symmetry is a good or very good, chances are a few of your small facet angles may be a TAD off (or more if your symm is only 'fair'), and that will change the way the diamond performs in real life too. Cool info to know!