Devin guides you through step-by-step instructions for faceting a rectangle cut amethyst.
Now that the pavilion is done, it is time to cut the crown. To do that we have to "flip" the rough on the dop and cut the other side. We have to remove the dop from the quill so that we can flip the stone over but you don't want to lose the positioning of the stone or it will be lopsided! We'll use a transfer alignment fixture to save our relative position so we can return to it after the transfer. Set the cutting angle to 90 degrees and the degree to the starting degree for the design. That is usually the highest number of the index gear you're using. Lower the mast height until the girdle facet brushes smoothly across the transfer alignment fixture. Make sure you always use the same grit lap so that your alignment fixture doesn't contaminate your laps.
The cutting angle is determined by the faceting diagram you're using to cut your gem. At least I hope you're using a diagram! Otherwise you're doing an abstract and that works much better with an oil and canvas. Consult your faceting machine owner's manual if you're having trouble figuring out how to set the cutting angle for your machine.