Octagon Dop — Pre-Shaped Mounting for Octagon-Cut Gem Blanks
Octagon Dop — Pre-Shaped Mounting for Octagon-Cut Gem Blanks
A faceting accessory with eight-sided end profile, used to align rough during cutting of emerald-shape and octagon stones
An octagon dop is a dop stick fitted with a pre-shaped octagonal end designed to hold emerald-cut or octagon-cut gemstone blanks during faceting. The eight-sided profile of the dop matches the intended outline of the finished stone, simplifying alignment and reducing the need for extensive preforming of the rough. Octagon dops are typically machined from brass, aluminium, or stainless steel and are attached to the quill of a faceting machine via a standard collet system.
Function in faceting practice
Faceting begins with mounting a piece of rough on a dop — a metal stick that holds the stone during cutting and polishing. Standard dops have flat or rounded ends; the cutter glues the rough to the dop with wax or epoxy, then orients the assembly on the faceting machine. For most cutting work, a flat-ended dop is sufficient; the cutter establishes the orientation through indexing and angle controls on the machine.
For octagon-cut stones, the pre-shaped octagon dop offers practical advantages. The flat facets of the octagonal dop end provide reference surfaces against which the cutter can orient the rough or the partially cut stone, ensuring that the eight-sided outline of the finished stone aligns with the dop's geometry. This simplifies the establishment of the girdle outline and provides a reference for indexing during the cutting of the crown and pavilion facets.
Practical use
Octagon dops are sold in matched pairs (one for cutting the pavilion, one for transferring to cut the crown) or as single dops for one-step transfer methods. The cutter mounts the rough on the pavilion dop with the desired orientation of the table or critical pavilion features, cuts the pavilion to completion, then transfers the stone to the crown dop using a transfer jig that maintains alignment.
The dop sizes available range from small (suitable for stones of a few millimetres) to large (for stones above 20 mm). Cutters select the dop closest in size to the intended girdle outline of the finished stone, with the rough held centrally on the dop to allow material removal in all directions during cutting.