Facet design alteration

Hi all. Bit of a technical one so I am not expecting many replies. I have taken this design - http://www.facetdiagrams.org/database/files/pc16006.html -
and have modified the crown angles in GemCad to suit a topaz. I chose this design because it best matches a rather tricky and quite large piece of rough I am working with.

Original design is RI 1.54 and I have changed it to suit an RI of 1.61 for topaz.

The result has yielded a number of crown angles that are below the the critical angle and many of these angles are in decimal integers. My facet head on the machine isn't accurate enough to match these angles with any kind of accuracy. Is it ok to round up and down for the close ones? Is this even going to work or am I just wasting good rough?

I have checked the design in GemRay and it seems relatively good. Is this software reliable?

General consensus is GemRay works and the few times I have used it the results are good. Replaces BOG.

How did you convert diagram?

The pavillion angles are the one's you really need to worry about - generally, but since it's original for Quartz it should not be a problem. The more the angles are out the more error you will incur. The pro's will just cut on the fly and not really care.

Thanks for responding. I used the edit scaling function in gemcad. Do you think it will be ok to round up and down the angles to the nearest whole number? Most are only out by .3 or less of a degree. Its more the ones that are in the .5 range I am concerned about. Will this possibly throw out the facet meets?

Normally I just cut what ever the diagram says because topaz is pretty close to quartz but this piece should come out flawless and depending on the depth of the design I should yield around 15-20+ carats so I want it to be as close to spec as I can get it.

Also I want to send it away to have it evaluated by a professional. Sort of a test to see if I'm cutting well enough as I have a friend who wants me to cut some really deep blue aquamarines.

Will this possibly throw out the facet meets?

Click to expand...

The question is how much it will throw them out. That I don't know but it will. The problem is the error can, if not dealt with appropriately, send you on a wild goose chase that will finish in a lot of bad meets. In short, yes it will affect your meets.

Use GemRay to calculate the angles. Select R.I. Hit the optimize button (several times). Replace old angle in GemCad with new calculated angle from GemRay. GemCad will do the rest.