Home > Advanced Diamond Information > Diamond Cutting > Stages of Cutting Rough
Stages of Cutting Rough
This sawed half of an octahedral crystal will be roughed in before it is girdled. The table will lay where the large saw plane exists here.
The sawed half has been glued on to the girdling machine dop and is ready to take a preliminary girdle.
This illustration represents a diamond that has been completely blocked and is ready for the brillianteering process. (This is also a finished single cut--17 facets).
For rough, the stages may be broken down as follows:
(1) Laying out the diamond, which would include placing windows to determine inclusion locations. The goal of the planning process is not only to preserve maximum weight, but also to achieve it with the highest possible clarity. The cutter does not want to end up with an inclusion in the culet of the diamond that has the potential of reflecting up to twenty-four times. The general rule of thumb is to lay out the stone inside the maximum spread. If the stone is a makeable (whole stone, not sawed), the table would be opened up, thereby designating the general layout of the finished diamond.
(2) For a nicely shaped octahedral crystal the next probable step would be sawing. If the cutter has placed a table on a whole stone then sawing will be very unlikely, since the table would be located where the two halves actually meet (the saw plane). There are heavy saw lines across these planes which give the cutter an indication of where the grain lays during the cutting process, and also where the culet is to be cut at the opposite end of the stone. The cutter will frequently choose to saw the diamond off-center, obtaining two different sizes in the sawed halves, and two different sizes in the finished stones. For instance, instead of getting two 0.88 carat finished pieces out of the sawed halves, the cutter could opt to saw it so the finished products will be a 0.95 and a 0.81, or perhaps a 1.00 and a 0.76 ct. Either way would net the cutter greater profit, since the latter two of the three scenarios attains larger size categories and more value.
(3) Roughing-in a piece of rough could be considered part of the laying out process (step one) or not. In a sawed half of a crystal, the sawyer (an artisan who specializes in sawing) has committed the layout of the stone in choosing the saw plane. Material is then cut away on the scaife, in part to shorten the girdler's work time. It is also an easy way for the cutter to keep the scaife sharp, with the larger amount of material being removed in these earlier stages. Both the top and bottom of the stone are roughed-in as much as possible, without going too far. In a sawed stone, the girdle will usually include four four-point grain convergences. This makes it more difficult for the girdler to round the stone, because of the extremely hard areas in these four-point grain convergences. (Often called four-point orientations, for that reason).
(4) Girdling is another specialty. It is common for girdlers not to be adept at other aspects of cutting, polishing, sawing, etc. These are the specialists who girdle the stone into its finished circular shape. This is a lathing process in which the girdler cements the diamond onto a brass dop and attacks it with another industrial quality diamond as it rotates on the girdling machine. The gem diamond is adjusted slightly by tapping the eccentric chuck. This allows the girdler to attain maximum spread, which is usually indicated by leaving at least two opposite naturals on, or close to, the girdle. The double spindle machine is a slightly more complex design that accomplishes the same purpose. Often the girdler will put on a preliminary girdle, and the cutter will rough it in further. Then back to the girdler, who will put on the final girdle.
(5) Once the final girdle is in place, the blocker goes to work on it. On a makeable, he may first opt to open up the table further before going to work on blocking the crown. After he is satisfied with the first four facets being in-square, he proceeds to the last four main facets of the crown. The pavilion is then blocked in with eight main facets. If the cutter opts to cut a culet on the stone this would typically be done after the first two facets are in place on the bottom. After each facet is cut to the proper size it is placed in the larger, outside smoothing ring for final polishing. Occasionally a cutter will opt to wait on the smoothing process until he is certain that no minor adjustments of the layout will have to be made. Depending on the shop, the crown and pavilion blockers may be separate specialists.
(6) Once the blocking is complete and the table is final (in size), the brillianteerer goes to work on the sixteen top halves (upper girdle facets). Then the sixteen bottom halves (lower girdle facets) are cut into place. Next, the table is polished before the stars are cut into place -- which finishes the diamond. Again, there could be three different specialty cutters for the three stages of brillianteering.
