I am studying faceting and I am wondering how to cut calibrated size gems out of rough to get exact accuracy?
I personally use an automatic preformer to shape the rough, then measure the stone with calipers repeatedly throughout faceting. The skill is in planning ahead for the amount to remove with each lap to end up at the desired size and fully remove all damage from each grit within a reasonable time. I myself haven’t fully mastered this yet but my gems have been able to be set in commercial mounts anyway since there’s some leeway. Good luck!