Setting an Oval Cabochon Pendant

Several milestones mark the path in learning to set gems. Knowing how to set a heavy bezel with a punch is one important step. When setting thin bezels, a rocker can be used; when more force is needed, a pusher is employed. But when the metal is too thick to merely push into place, greater force must be applied in smaller areas at a time. Because this bezel is 14k yellow gold, it is too hard to push the metal inward without having it bounce back. This calls for use of a setting punch.

Setting punches are made of tool steel. A square or round rod about 3 mm to 4 mm in diameter is cut to about 100 mm (4 in.) in length. Both ends are flattened, and then the working end is filed or ground down to a long taper. The final working face should be a rectangle about 1.5 mm x 2.5 mm in size. Leave a filed texture on the face for gripping, so that the punch does not slip around and damage the stone.

1. Prior to setting, most bezels are left taller than needed so they can be cut down to the proper height—i.e., the minimum height required to grab the sloping sides of the stone. If you cut the bezel down too far, there will not be enough metal to hold the stone securely. If you leave too much metal, it will be more difficult to set the stone, and more of the stone than necessary will be hidden. The idea is to cut down the bezel to the lowest point possible. Using a slide caliper, check to see that the top of the bezel is level with the base; correct by filing if necessary. To gauge the amount of metal to be removed from the top of the bezel, place the stone on a sheet of metal the same thickness as the seat in the setting and put the sheet and stone next to the bezel. Now visually mark the height requirement.

2. Use a pair of steel dividers to inscribe a line at the desired height. Do this by setting the dividers to the correct opening and then, with one leg riding along the top edge, let the other leg scratch a line all around the outside of the bezel.

3. Use a jeweler’s saw to cut off the excess. However, don’t just saw across the entire bezel in hopes that the line will be accurate and straight—it won’t. Instead, place the saw blade above—not on—the line, and make a notch. Then lengthen the notch, slowly cutting and extending the line all the way around the bezel. Continue to saw around and around the bezel slowly, as the cut gets deeper and deeper, until finally an oval ring of metal lifts off.

4. Use a fine-cut flat file to remove the saw cuts and irregularities on the top edge of the bezel. Barette files, half-round files, and flat files all have a flat surface that will do the job. Using a fine-cut file (cut #4 or #6) on a thin bezel is safer and less likely to grab than a coarse-cut file. It also leaves the top surface flatter and more refined.

5. Since filing always leaves a burr or rag of metal, use a sharp triangle scraper to cut the excess off. Remove the burr on the interior as well as the exterior of the bezel.

6. It is important to hold the work very firmly when setting the stone in the bezel. One traditional way is to affix the work to a dop stick—a wooden dowel with sealing wax on the end. Dop, sealing wax, and lapidary cement are all pretty much the same thing, coming in different colors that indicate different levels of elasticity/hardness.

To prepare a dop stick, begin by dripping some hot dop onto the dowel’s end surface. Use only a cool reducing flame (no oxygen) when melting dop. This could be the flame from an alcohol lamp or from a torch without oxygen or air mixed in. (Warning: Hot dop burns skin. Never allow hot, “glossy” dop to drip on your hands.)

Slowly build up a layer of dop and periodically shape it against a cold steel block, leaving it with a flat, level surface. Now warm the pendant, while holding it in tweezers. Both the dop and the work must be warm in order for the dop to adhere. Place the setting in position in the dop. If the metal is the proper temperature, the dop will stick and creep up the sides a bit. After the dop has cooled, use a knife or graver to remove any dop that rose above the seat level on the interior.

7. Place the stone into the bezel. Sometimes, if the stone is slightly loose, it will jump around—and perhaps even bounce out—during setting. To keep it in position, make a “setting snake” out of the same sticky wax used to transport stones. Take a small dab of this wax and roll it into an elongated little twist, like a snake. Now place this over the stone and down the sides of the bezel, holding the stone firmly in position.

With the work secured, clamp the dop stick into a vise, engravers block, or Benchmate rotating vise (shown). When setting ovals, always close the “ends” first. With a chasing hammer in one hand and all the fingers of your other hand holding the setting punch in place, tap the top of the tool, driving the face into the top edge of the bezel.

The angle of the punch should be about 60° to 70° at the beginning, which forces the metal inward as well as over the stone. Make sure the tool never touches the gem: Always leave a sliver of gold in view between the punch and gemstone. Begin at the ends of the oval and close just a small amount over the stone, until both ends are locked in place.

As soon as the metal has been forced inward, raise the punch to about 80° to close the inner lip of the bezel against the stone. This technique crimps the metal over the stone by using the impact and leverage of the punch, now held close to vertical. The face of the punch leaves a planished (flat) bevel on top of the bezel, angled down about 10° from horizontal.

8. Close in the sides next, using the same technique: 60° to 70° at first, followed by 80° at the end. When you are finished, the bezel should have four flat-looking sides, with rounded corners.

9. After the four sides have been brought in toward the stone, use the punch to close the metal in the “corners” that remain, using the same sequence. When the entire bezel is down, use the punch to planish (flatten) the surface closer to the desired shape. This should leave it with a flat, even bevel—about 10° below horizontal—all around the top edge of the setting. The metal should make full contact with the gem.

10. Prior to cleaning up the bezel, or at any other time when desired, protect the delicate bale by covering it with a layer of masking tape. This works as a reminder to be careful, as well as actually protecting the bale from being accidentally scratched or filed.

Use a safe-edge square needle file (cut #4 or #6) to refine the bevel. This is a normal square needle file on which one of the four sides has been ground away and polished. In preparing this file, it is also important to remove the teeth from the two adjacent corners as well, and polish them too. Although it’s always best to keep files away from stones, it’s unlikely that a polished safe edge and corners will damage a hard stone.

With the polished face riding next to the stone, use the cutting face to lower and perfect the beveled edge. Take long, continuous, curving strokes, leaving the bevel at an even angle all around, about 10° below horizontal.

11. In preparation for polishing, bring the bezel to a fine finish. In order to perfect the flat bevel, use a pumice wheel, which will not damage most stones (check first). This is a rubberized abrasive wheel that has been charged with pumice. When using it, the flat edge of the wheel leaves a flat edge on the bezel. Shape the wheel periodically against a flat file to keep the edge flat and crisp. Use long, sweeping, continuous strokes with the spinning abrasive wheel.

12. Remove the work from the dop by placing it in a freezer for about 10 minutes, and then cracking it off. Acetone (which is toxic, so handle with care!) can be used to dissolve any dop that will not come off easily. Buff the work with tripoli and then polish it with rouge.

© 2003 Alan Revere

First publication rights assigned to JCK magazine.

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.