Pre-forming and Dopping

Pre-form your rough before dopping, with the jamb peg you are cutting to make best use of your rough and not cutting to a set ratio as in a diagram.

These dopsticks are pointed, no flats or V's to aid in dopping. Originally they would of been used with UV setting adhesive, the pavilion will be dopped as the crown is cut first.
One size fits all.

The stone is dopped allowing around 1/3 of the depth for the crown. Emerald and square cuts can be done on the machine. Oval, pear's etc. are pre-formed by eye. You will need an alternative method to pre-form rounds.

The table of the pre-formed stone is pressed against a flat plate to align it on the dopstick. Check the stone is centered, if not just warm it up and move the stone. It doesn't have to be 100% perfect.

Always Crown First!

Most mast and hand piece cutters will cut pavilion first. But with the jamb peg the crown is cut. If you allow around a third of the stone for the crown and keep the table at at around 50% you won't go far wrong. Try not to over cut any of the mains as you might end up short of stone when doing the pavilion. Because of the repeatability when using the jamb peg you can always go back and touch up facets if needed.
Because the preform is dopped by eye it's not always 100% centred on the dop stick, but by cutting the crown first the table is level, all the facets look even and the girdle is good, so the finished crown will always looks great.
When the pavilion is cut there may be minor angle changes because the stone is slightly offset, the culet point may not be centre but I doubt anyone will notice, but you will have a good girdle and the overall appearance of the stone will be good . But if this was the crown any errors will be obvious. So that's why crown is cut first.