REPLACING PRONGS

Jewelry components such as prongs receive heavy wear and often need repair or replacement. Here's how to do it

by Alan Revere

with Werner Cronauer & Edward J. Freidman

Photos by Barry Blau

Most people think metals such as gold, silver and platinum are strong and enduring. Indeed, for the most part, they are. However, extended use will wear away precious metals just as mountains are eroded by centuries of wind and rain. Look at a well-used coin and the impermanence of these "durable" metals becomes evident.

Some jewelry components receive greater wear than others and often need repair by jewelers. Due to their exposure, pendant bales, prongs and ring shanks wear down more rapidly, until they must be rebuilt or replaced. Prongs, which may hold valuable gems and diamonds, are particularly vulnerable. It's a good idea to inspect prongs periodically to make sure they are doing their job and replace or rebuild them as needed. Depending on the design of a piece of jewelry, replacing prongs can be relatively simple or quite complicated. This kind of work requires precision layout, fitting, soldering and filing as well as the techniques of stone setting.

In this project, master goldsmith Alan Revere explains how to replace a set of four heavy gold prongs in an onyx ring. Although specifics may vary from job to job, the techniques are the same for a wide variety of prong repairs.

(Photos accompany this article on pages 136-140 of the December 1995 issue of JCK.)

1. The wearer brings an onyx and 14k gold ring into your jewelry store, questioning the security of the gemstone and the quality of the craftsmanship. The ring has adorned her right hand continuously for years, so it has seen a lot of action. The prongs are worn so thin that one has broken off and only three slivers of gold prevent the stone from falling out.

You pick up a loupe and examine the ring slowly and carefully as you ask yourself such questions as: What are the materials? What is the gem? How was it made? Was it well made? Where are the solder seams, if any? How worn is it? Has it been repaired before? Were previous repairs done well?

Take a close look to determine the exact problems that need correcting. Imagine the steps, procedures, materials and risks to be considered. Estimate the time and materials costs and the price to be charged. The cost should be weighed against the value of the item.

With the information you've gathered by observation, you can tell the customer that her ring was cast in one piece from a wax model and that the craftsmanship is good. The ring will last a long time, but will need periodic maintenance based on how much it is worn. You explain that the ring wears down a little bit every time it touches another object. Even bed sheets can be abrasive when they rub against gold jewelry every night. Wearing a ring when sleeping adds thousands of hours of constant rubbing each year to the scuffing, stroking, scraping, knocking, nicking and bumping it suffers during waking hours. A year of such abrasion equals one rub against concrete.

It is normal to need some repairs to the prongs and shank; such maintenance will add years of life to a ring and insure that the stone is protected. You remind the customer that a Florentine texture once decorated some parts of the ring, although the pattern has been worn away and is now barely visible. You offer to re-engrave the pattern as well as replace the prongs and the customer gladly agrees to go ahead with the repair.

Recheck the ring carefully and fill in the blanks on a job envelope. Make sure that materials are noted accurately and the instructions are clear. You don't want any surprises when you sit down at the bench to begin working. Mistakes made here can be very costly; once you accept an item of jewelry for repair and offer a receipt, you also accept responsibility to return it to its owner. More than one customer has returned to a jeweler claiming that the item he or she received was not the same one brought in for repair.

2. The three thin prongs can be pushed away easily with a prong pusher, a flat graver or even a knife blade. Remove the onyx, wrap it in a paper bindle and place it in the job envelope. Put the ring in an ultrasonic cleaner to vibrate and loosen built-up dirt. Next use a steamer to blow away any remaining debris. (If you do not have these two pieces of equipment, vigorous scrubbing with tooth brush and hot soapy water works almost as well.) Use a pair of flush-cutting nippers to clip off the prongs; save the clippings for eventual recycling.

3. Use a large flat file to adjust the seat until it is flat, stopping as soon as you see one large clean oval seat. Place the stone onto the flat seat and accurately scribe a line around it, indicating the exact perimeter.

4. Locate the four "corners" by eye and lay out the positions of the prongs. Make the replacement prongs from a rectangular 14k yellow gold strip that is slightly larger than the old prongs. To mark the exact size and position of each prong, place the strip flat on the seat, with one end aimed at the center and the other covering the position of a new prong. Scribe the width where each prong meets the perimeter. Next turn the strip on edge, place it over the location and mark the thickness of the metal perpendicular to the width lines to show exactly where the prong will be attached. The majority of the prong is outside the perimeter, but a small portion overlaps into the perimeter.

While the prongs could be simply soldered onto the flat surface, carving a notch and then soldering each prong into a frame makes a stronger joint. The notches can be carved in several ways, using a saw, file or graver, depending on the item. In this case a thin, tapered cutting burr is very quick and accurate. Methodically excavate all four notches, making sure to stay within the outlines. Carve a bit on one seat and then go to the others, bringing them all to their final shape stage by stage. As you get closer and closer to the final size, check the fit more often so that the new prongs fit tight enough to be held in place by friction.

5. If the seat does not hold a prong in place, use a pair of third hands (locking tweezers mounted on a stand) to hold the assembly for soldering. Mount the ring in one pair, while a second pair holds the prong exactly where it should go. Use hard solder to secure the prongs one by one. Remember that the ring and prong must reach the same temperature at the same time for the solder to flow properly. Since the ring is much heftier, it will need more heating than the relatively thin prong. It is okay to be generous with the solder to insure maximum strength; any excess either will not show or can be removed later.

After soldering, pickle, rinse and check the seams. Clip or saw the prongs to a generous height; the extra material provides added leverage when pushing the prongs over the stone. Trim and finish the sides of the prongs as needed and polish the entire ring.

6. Checking the fit of the stone, you determine that the prongs, as planned, are a bit too close together. Use a knife-shaped needle file with a polished safety edge resting on the seat to carve at a slight angle into the bases of the prongs from the inside. When setting, remember that metal bends at its thinnest point. Filing in this way will insure that the prongs close onto the stone from their bases.

7. Engraving is a very old art form that encompasses a broad field of techniques too varied to be covered in this article. For instruction, contact a professional jewelry school. Although books and videos can be useful, engraving is unusually difficult to learn on one's own.

Florentine textures are made with specialized gravers as the last step before setting. Gravers are very useful precision chisels which can remove metal in places where no other tool will fit. When mastered, they have many applications including stone setting, texturing, decoration, monogramming, cleaning, fitting and as a background for enameling.

Gravers come in a vast range of shapes and sizes that vary from supplier to supplier. A Florentine graver (sometimes called a line graver) has a flat bottom with many thin grooves that impart several parallel lines to metal surface. Assuming you have knowledge and experience in using such tools, here's how to reapply the texture.

Secure the ring in a ring clamp or engraving block, making sure not to crush thin or weak areas. Brace the work against a bench pin for stability and press your thumbs together for security. Slowly push the graver across the surface, incising polished lines and removing threads of metal along the way. Repeated short strokes are easiest and leave many parallel lines behind. Cross-hatching, the most common Florentine pattern, results when a second series of cuts is made across the first. A random cross-hatched pattern is easiest to accomplish and much more interesting than a perfect grid.

8. A traditional engraver's block is an alternate device for holding work securely. Its weight and multi-directional positioning give you two hands free instead of one. Engraver's blocks usually come with a kit of adapters to clamp a variety of items without marring them. In this case, a strip of heavy leather easily protects and a tapered wooden dowel supports the ring from inside. Pick up and position the stone by using a wooden dowel with some sticky wax on the end. The seat must be level or the stone is likely to crack during setting. Use a file to make final adjustments on the seat. Check by pushing the onyx from various points on top; it shouldn't rock no matter where contact is made.

9. When setting gems, remember that their durability varies. Refer to a chart for specifics of the material you are working with. You can use several methods to set the stone. For example, chain nose or flat pliers can be used to squeeze the prongs inward or prong pushers to apply force with greater accuracy. In this project we will use a traditional setting punch and chasing hammer because they exert a precise force with the greatest leverage. The punch is made from 4mm square steel about 100mm long. One end is tapered to a rectangular face measuring 2mm by 1mm. The unpolished face is textured with a file to prevent slipping, and the steel is left unhardened. Hold the punch with all of your fingers either wrapped around it or braced against the work for stability.

10. The setting process involves two stages. First, move the prong up against the stone; second, fold the tip over the stone. As always when setting, alternate working on opposite sides, just as you tighten the lugs when changing a tire. Never complete one prong before the others are at the same stage.

Place the tip of the punch against the top of a prong at an angle less than 90º. Use a chasing hammer to tap the punch a few times, pushing the body of the prong against the stone. Repeat this process on the opposite prong and then on the two remaining prongs. Tap lightly at first, then increase the force gradually to move the prong. If the metal springs back, raise the angle of the punch so that the metal is compressed as it is moved against the stone. Hold the work up against a bright background and look for gaps where the prongs do not lie flush against the stone. Adjust as needed.

11. For the second stage of setting, remember that metal bends at its thinnest point. When the bodies of the prongs are against the stone, file the tips to the correct height and angle so they can be tapped over the stone.

12. Now raise the punch to 90º and tap the tips so that they make full contact with the stone. As the prongs near their ideal positions, use less force. This will spread the metal over the prong without actually moving the whole prong. Again hold the work up to a bright background to check for gaps between the prongs and the stone, adjusting as needed.

13. Use a very fine (Cut 4 or 6) needle file with a safe (polished) edge to finish the prongs. Leave the metal as hefty as possible as you remove any sharp corners and round the tips slightly. Go to the polishing lathe to buff and polish any areas of the ring that need it.

First publication rights assigned to Jewelers' Circular-Keystone.