18 steps to success

A fancy-shaped stone, like a pear, requires special setting procedures. For one thing, the girdle and shape of the stone are different at the tip and the back of the stone, so two distinct types of prongs are needed in the setting. The sharp points of pear-shaped and marquise stones usually are set in large “V” prongs, while the sides are secured in round prongs. Follow along as master goldsmith Alan Revere explains the ins and outs of pear setting.

  1. Once the side stones are set (see “Practical Stone Setting, Part VII,” JCK, April 2004, p. 117), focus your attention on preparing for the center gem, in this case a 7-mm x 5-mm pear-shaped stone. Check the stone for damage and examine the cut. Look at the girdle. Is it thin or thick or variable? Is the slope of the pavilion uniform? Is the girdle level with the table? Note your observations on the job envelope. All of this information must be considered when planning to cut seats for the stone. Regardless of the shape, the seats in the prongs must be carved to fit.

  2. File the tops of the prongs, bringing them all into one flat plane. Place the stone on top and look at it from above and from the sides. The back (round) prongs can be moved in or out to accommodate small variations in stone sizes—one of the advantages of prong settings. Adjust the prongs so that the stone sits on the inner part of the top of all prongs.

  3. Visualize the point where the girdle will rest when the stone is in the setting. In order to lay out the height of the seat on each prong, it’s helpful to inscribe very light guidelines. Set a pair of dividers at the correct distance between the tops of the prongs and the projected height. Use the dividers with one leg resting on the top of a prong and transfer this measurement all the way around each prong very lightly—in fact, so lightly that the finest sanding will remove them.

  4. Move the two back prongs out slightly with a pair of chain nose pliers. Grab the entire length of each prong and slowly guide it out to allow access to the interior. This permits you to cut the seat before you push the prong back onto the stone.

  5. Depending on the cut of the stone and the height at which you are setting it, it may be advisable to remove some metal from the inside of the pear-shaped seating wire. If the pavilion is particularly thick, the setting is particularly shallow, or for some other reason it looks like the lower half of the stone will hit the seating wire, trim it back. Use a 3-mm bud bur to carefully carve back the wire as needed, leaving a flat angled facet on the interior. Fine needle files and/or gravers also can be used to make this cut and/or to work in difficult areas.

  6. Next, use a 3-mm hart bur to carve the seats into the back prongs. Stabilize your hands on the bench pin and hold the work securely. With the girdle of the bur held in line with the mark that represents where the girdle will sit, bring the spinning bur very lightly into contact with the prong. This requires a higher speed and lighter touch than normal. As everyone learns quickly, if your hands are not absolutely firm the bur will skip around the prong uncontrollably, leaving a gouge. Holding the ring in a wooden ring clamp is helpful. Another trick is to hold a piece of wood on the outside of the prong, where the bur would like to skip toward, to prevent the bur from going around the prong.
    The cuts should be even and level, about one-third of the way deep into the prong, and never more than halfway. Unless the girdle of the stone is the same shape as the bur, it will be necessary to use the bur to carve away more metal from the prong below the girdle. Use the bur to carve upwards to the mark, thus accommodating a thick girdle and leaving an angle to match the stone. Use a fine file to remove the flashing.

  7. Use a 1.5-mm hart bur to cut the seat for the point of the stone into the V prong. Hold the work securely and, with the shaft of the bur vertical, bring the spinning edge of the bur into the V at the mark. Cut into the V and then cut to the left and right a little bit, out to the ends of each side of the V. As before, use a medium to high speed and a very light touch to prevent the bur from spinning out of control and wrapping around the prong. Prevent slipping by holding a piece of wood on the far side of the V. If the girdle of the stone is thick at the point, wiggle the bur up and down as needed to accommodate the shape. Use a fine file to remove the flashing.

  8. The V prong should hold the stone at the sides near the point, while the point itself floats with no contact at all. To accomplish this, use a 0.5-mm ball bur directly into the point. As before, if the stone’s girdle is thick at the point, wiggle the bur up and down.

  9. Prior to inserting the stone, clean up all flashing from filing and/or burring. Remove any tool marks or irregularities on the surfaces of the metal, especially around the prongs and seating wire, which soon will be inaccessible. Now is the best time to polish the interior and exterior in areas that will be hidden by the stone. Use sticky wax to transport the stone into the setting, point first.

  10. With the point in place, use a pusher with a 2-mm square face held against each of the back prongs to close them inward. Beginning with the pusher at a low angle (nearly horizontal), move each prong inward against the stone.

  11. Reposition the pusher on the tip of each prong. As you raise the handle, push the prong closer as the tips tighten snugly over the stone. Check to make sure there is full contact between the prongs and the stone at all points.

  12. Focusing on the V prong again, note that the opening is larger than necessary and the angle of the V is greater than that of the stone. Carefully position the tips of a pair of chain nose pliers as you grip the outer edges of the V. Do not let the pliers slip.

  13. Close the V prong by squeezing evenly from both sides until the angle of the V matches that of the tip of the pear. Because the tip of the stone is floating, there is no contact to worry about. In fact, closing the V results in the V prong pulling away from the stone at the tip, as it grabs the sides of the tip firmly and safely.

  14. The top of the V prong can be trimmed with either a saw or file, leaving it flush with the table of the stone. Using a 4-cut barrette needle file, establish a flat facet on each side of the V. Each facet should be the same angle as the crown of the stone, and the two facets should come together at a crisp, straight, “mitered” corner in the middle of the tip of the V. Finish these facets with a 6-cut file.

  15. Each side of the V prong should have another small facet or “bright cut” inside the larger ones you just filed. It should be at 90 degrees to the major facet and act as a reflector, throwing more light into the stone. Use the tip of a flat graver, held perpendicular to the crown of the stone, to neatly trim the inside of the tip of the V prong. This is a shaving process whereby several strokes are taken, each one skimming off a sliver of metal. Several passes are needed to yield crisp, flat, engraved bright cuts.

  16. Use a pair of fine-nose nippers or flush-cutting pliers to trim down the excess metal on the back prongs, leaving it the same height as the table.

  17. Finish the two round prongs with a cup bur. Trim and shape the metal as you work the bur in a circular motion around the tip to yield perfectly matched hemispheres. The tips of the prongs should be about 70 percent to 80 percent of the height of the crown of the stone. In other words, generally the prongs should be a little lower than the table.

  18. Detail the setting with rubberized abrasives as needed to take out tool marks. Use a flat felt wheel to polish the sides and top facets of the V prong. Use brushes and buffs as necessary to polish the rest of the ring to completion.

The procedures in this article are standard practices for bench jewelers at this time. If not executed properly, however, they can cause harm. Neither the author nor publisher is responsible for injuries, losses, or damage that may result from the use or misuse of this information.

©Alan Revere. First publication rights assigned to JCK magazine.

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