Part 23: Bright Cut Box
NOTE: The procedures described in this article are standard practices for bench jewelers. If not executed properly, however, they can cause harm. Neither the author nor publisher assumes responsibility for injuries, losses, or damage that may result from the use or misuse of this information.
Along the way to learning the art of stone setting, certain milestones mark the trail to competency. One is the Bright Cut Box Setting, which requires myriad skills—layout, drilling, seating, raising beads, beading, and bright cutting. These techniques have been documented in prior articles that have appeared in JCK.
In this demonstration, I combine all of these skills to set a 4 mm round cubic zirconium into a copper plate. This style of holding small stones is called bead and bright cut setting. When multiple gems are set close together in the same manner, it is called pavé setting (pavé is French for paved?).
Safety Alert: Gravers are extremely sharp and, if used improperly, can cause serious injury. Be sure that your hands are firmly secured and safely protected from the graver at all times.
1. For this demonstration, the stone will be set into a thick copper plate. Copper is inexpensive and responds in a similar way to gold and platinum, the metals most frequently used for such applications. Begin with a 1.5 mm thick plate, approximately 25 mm square. Prepare the surface with Scotch Brite®. Use a straight edge and scribe to lay out diagonals from corner to corner so that you can locate the center of the plate. Make a tiny indentation with a center punch and chasing hammer.
2. Start with a 1 mm bit and drill incrementally larger holes, 2 mm followed by 3 mm.
3. An engraving block is ideal for holding this project. If one is not available, there are several alternatives. You can use a smaller piece of metal held in a ring clamp or bend a corner of the square at 90 degrees and grab it in a hand vise.
Once the work is firmly held, use a 4 mm round bur to open the hole and begin the seat by removing metal until the full diameter of the bur is almost buried. The advantage of this bur is that it removes a lot of metal quickly in preparation for refining the seat in the next step. Flip the plate over and use this bur to clean up the rag left from drilling.
4. Now use a 4 mm setting bur to carve a seat and vertical wall. If a bur the same size as the stone is not available, select one slightly smaller and ream the hole a bit to allow the stone to enter. These burs match the profile of the stone, so the seat should match, too. Burr a bit as you check periodically for the fit. The stone should drop in with a little contact all around and sit with the table barely above the level of the metal. For a stone this large, placing the table flush would mean that the girdle is too low, which makes subsequent steps more difficult. In general, stones 3 mm and smaller can be set flush.
5. Several different approaches can be used for the simple task of laying out a 5 mm square around the 4 mm hole. In fact you might lay out the square first and then drill. Each procedure has its advantages and disadvantages. In this example, set a pair of dividers at precisely 5 mm. Now hold the dividers at a low angle against the metal and lightly place both tips on the surface, with the hole centered between them. This measurement is one of visual estimation, which can be quite precise, especially after some practice. When the tips are in the right place and also closest to the sides, press them into the metal. You can also lift the handle and press the tips downward, leaving tiny nicks. Repeat for the other two sides. When this layout is complete, the four nicks are each 0.5 mm from the hole.
6. Now reset the dividers to the distance between a nick and the closest wall. Drag the dividers along the edge to mark a parallel line running through the nick. Reset the dividers for each side and repeat the process. The result is a perfect square with sides 0.5 mm from the edge of the hole, allowing the 4 mm stone to sit in a 5 mm box.
|Fig. 6. Dragging the dividers to lay out the square|
7. Place the stone into the seat and check for level and height. About one-quarter of the crown should be visible above the surface when viewed from the side. Rotate the stone so that the octagonal table is aligned with the square plate. Use a square graver to begin raising metal for the beads. (Note that using gravers requires preparation and practice, as outlined in prior installments of Practical Stone Setting.)
Place the tip precisely in the corner of the box. Then slowly and carefully push it straight ahead, in and down at about 45 degrees, gathering metal as it glides forward. When the gathered metal is just about to bulge up against the stone, stop. Pushing further at this point could tip the stone. The idea is to bring the metal in close, but without contact.
8. Spin the engraving block around and repeat the same step on the opposite side of the stone. When there are two raised beads touching opposite sides, the stone should be secure. Continue to tighten the stone by pushing one bead further so that it begins to bulge up against the stone and then over the girdle a little bit. Go back and forth, moving a little metal on one side and then the other gradually to prevent rocking the stone.
9. Once the stone is held at two points, test it by touching the culet from below with a fingernail, toothpick, or pencil tip. If there is movement, use the graver to push the beads further until the stone does not wiggle when touched. Now raise two beads for the other two corners and tighten until all four are secure. After moving the metal in at 45 degrees all around, lift the graver to about 60 degrees and repeat, tightening and securing the metal over the stone at four points.
10. Use a polished beading tool to shape and direct the raised metal beads into perfectly hemispherical balls. Select a beading tool that does not leave a rag around the edges. Size 12–14 will work well here. Very gently, place the concave tip over one of the raised pointed beads. Use a light touch and gentle rotation from above to begin to shape the bead, increasing the pressure as the hardened steel tool shapes the softer metal into a ball. Repeat for all four beads.
11. With the stone seated and secured by four hemispherical beads, it is time to remove the excess metal, leaving a bright and shiny beveled frame to enhance the stone’s appearance. This “bright cut” is standard fare for many stone settings, including bezels. It is used whenever diamonds are set into the surface of metal, individually or in clusters. The bright cut removes excess metal and leaves the surface with a mirror finish. The process requires the use of a flat graver in three separate steps to remove the metal, and then another to blend and even out the steps.
For a right-handed stone setter, place the left corner of a #41 flat graver precisely on the corner of the box, which has been laid out around the stone. Lift the handle a couple of degrees and point the left side of the graver toward the opposite corner. Tilt the face of graver as you lift the far side about 30 degrees. Once in this position, do not alter the graver’s orientation to the metal.
12. Brace your hands well. (Slipping with a sharp graver can be very dangerous!) Slowly and precisely, push the graver forward into the metal up to the base of the bead. As the graver cuts, it gets deeper and deeper, gathering metal up against the base of the bead. Stop just short of running into and shaving off the bead.
|Fig. 12. Flat graver pushed up against first bead, with gathered metal|
13. With the graver stopped, you are ready to flick away the rag of metal, which has been gathered. In a separate motion, use your thumb to lift and push the face of the graver forward quickly, flicking the gathered metal off. Once the graver is removed, the bright flat surface of the cut is revealed.
14. Place the graver back into precisely the same position at the end of the first bright cut, up against the first bead. Now slide the graver a few tenths of a millimeter to the right so it will miss the bead when pushed forward, in preparation for the second step. The idea is for the graver to move forward again, around the bead while cutting a second, longer bright cut section between the beads. With the graver lined up just past the first bead, maintain the same angle and lift of the graver as it is brought into position for shaving more metal around the stone.
15. While maintaining exactly the same lift and tilt, push the graver forward, making a second cut beside the first one. This may be made easier by taking a few very light and short cuts and then connecting them. Do not change the angle or direction of the graver as it slides through metal right up against the second bead.
16. Push the graver right up to the base of the second bead. After stopping forward motion, again use the graver to flick away the gathered metal. This reveals the second bright section of the frame around the stone.
|Fig. 16. Second bright cut section removed|
17. Now place the graver back into the position where it was at the end of the second cut, right up against the second bead. Again slide the graver sideways a few tenths until the tip of the graver clears the second bead. Maintain the same graver orientation, angle, and lift as you prepare to clear the final section into the corner.
18. Push the graver into the corner, gathering the last bit of metal along the sidewall. As the graver reaches the corner, it shears off the gathered metal. Often there is an audible “click” as the graver chops off the metal and meets the deeper corner cut made earlier by the square graver. All the while, the graver remains in the same orientation, so that all three sections align into the same plane.
|Fig. 18. Flat graver making the final cut into the corner|
19. At this point, now that the graver has been removed, all three sections are roughed out within the outline of the frame. There are also little bits of extra metal remaining to be removed, and the bright cut needs to be refined and brought into one reflective plane.
At this point, all of the steps have been outlined. The task that remains is to repeat the same sequence for each of the four sides. And then after the four sides have been trimmed, go back and rework the cuts on each side, bringing them all into one plane. Periodically refresh the beads with a beading, too.
20. When all four sides have been cut, trimmed, and refined, the square box around the stone acts as a dramatic frame. The beads are clear and round, and the bright cut sides are crisp and reflective.
© 2010 Revere Academy of Jewelry Arts
First publication rights assigned to JCK magazine