RB stat tutorial?

[alloamie]

I''m looking for some help when reading stats on RBs. Are there any charts or websites that will help me make sense of these numbers as I''m no expert.
Or are there guidelines to look for when picking a RB?
Thanks!

 

[neatfreak]

Here are some easy guidelines. Good Old Gold also has great tutorials on their website:

Bear in mind, the combos for crown and pavillion angles at the steeper and shallower ranges may need further examination.

depth - 60 - 62 ( although you can go deeper if all else is right, suggest a max of 62.6%)

table - 54 - 57%

crown angle -shallower 34 - 35% getting a bit steeper = further eval

pavillion angle - shallower 40.5 - 40.9 or 41 getting a bit steeper= further eval

girdle thin to slightly thick, medium, slightly thin are all fine, avoid extremes such as thin to ex thick.

 

[Regular Guy]

Hmmmm,

You are here (with 17 posts under your belt!).

See the tutorial under Knowledge, above (including the charts at the end...)

See the Cut Advisor, above, under tools.

Notes under my signature will take you there, and more.

 

[stone-cold11]

Just input the numbers required by the HCA and seriously consider stones scoring < 2.

Other than that, there is a AGA guideline, which gives a smaller number of candidates.

 

[late-start]

was going to suggest GoG as well

goodluck

 

[Lorelei]

Date: 12/1/2008 6:55:43 PM
Author:alloamie
I'm looking for some help when reading stats on RBs. Are there any charts or websites that will help me make sense of these numbers as I'm no expert.
Or are there guidelines to look for when picking a RB?
Thanks!

Add to the numbers Neat gave you below which seem to help other posters,

depth - 60 - 62% - although my personal preference is to allow up to 62.4%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

note - with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input - check as appropriate!

As the above implies, configurations depend on each other. A little give here can still work with a little take there.

With that said, here's a "Cliff's Notes" for staying near Tolkowsky/ideal angles with GIA reports (their numbers are rounded): A crown angle of 34.0, 34.5 or 35.0 is usually safe with a 40.8 pavilion angle. If pavilion angle = 40.6 lean toward a 34.5-35.0 crown. If pavilion angle = 41 lean toward a 34.0-34.5 crown.

GIA "EX" in cut is great at its heart, but it ranges a bit wider than some people prefer, particularly in deep combinations (pavilion > 41 with crown > 35).