Dopping

My dopping setup, all the usual bits and pieces. Dopping stones for the jamb peg is easier than with other machines, a lot more forgiving.

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.

Waxed dopstick ready for the pre-form

The rough is pre-formed first as this gives a good indication of the amount of usable stone you have to work with, allow around 1/3 for the crown and 2/3 for the pavilion. The stone is dopped to allow the crown to be cut first.

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.