This ring was always tight on Mrs. Ghirardelli’s finger. But as she was getting ready for a party the other evening, she could barely squeeze it over her knuckle. And once it was on her finger, she noticed that the ring pinched her skin like a tight corset.
“I guess I have put on a pound or two in the last few years,” she chuckles, handing you the ring at the jewelry counter. A check of her finger size and that of the ring confirms that chocolate must be one of Mrs. Ghirardelli’s favorite fruits.
Upon close examination, you determine that although this ring is not new, it still has a lot of life left. It is true that the shank has thinned with wear, but the metal holding the diamonds is still substantial. The directions on the job envelope are to size the ring up one size to 5 1/4. Considering the thinness of the shank, as noted on the envelope (1.4mm wide by 1.0mm thick), stretching is out of the question.
Clean the ring in an ultrasonic bath and steamer and examine it with a loupe. Since this ring is now 4 1/4, it is likely that it was once sized down, and there should be a seam. If you cannot find it, heat the back of the shank (without fire-coating the ring) just enough to discolor it. Because all alloys oxidize differently upon heating, the seam becomes visible, confirming your guess about prior sizing.
Your cut through the shank should be right on the seam. This way you remove all of the old solder. Steady the ring against the nub carved on your bench pin as you saw through the seam. If necessary, fine-tune the saw cut by filing both sides of the open shank.
In order to make this ring one size larger, a piece of gold 2.54mm wide has to be inserted (2.5mm is acceptable). Use a metric ruler, a slide caliper, or a ring-size gauge to set the measurement for the sizing as close to 2.54mm as possible; digital calipers are the easiest to read. Open or close the calipers until the desired measurement is reached, and set a pair of dividers against the outside of the small jaws.
Choose a piece of sizing stock to match your ring. In this case the shank is 1.4mm wide and so a piece of stock 1.5mm by 3.5mm provides a bit of extra material. Transfer the divider measurement to the stock by placing one leg against the long side of the bar, then lightly dragging the dividers along, making a parallel line at 2.54mm. This line only needs to be a few millimeters long, which is more than adequate for the 1mm thickness of the shank.
Either a file or a saw will work to trim the stock to the desired width. Sawing right on the line is all right, since the ring can be tapped up to the precise size later.
Slide the ring up a ring mandrel so the shank expands past the desired size of 5 1/4. Insert the sizing material so that the edges of it hold apart the shank ends, and then close the ring onto it by sliding the ring back down the mandrel.
With the ring clamped onto the stock, hold up the 2 pieces in front of a window or light and examine the silhouette. There may be wedge-shaped gaps between the shank and the stock; if so, use a permanent marker to indicate where the pieces do meet and adjust by filing where the pieces already fit. Check the fit frequently and when it is correct, leave the stock in place. Set the bar into
a third hand (stationary tweezers) with the ring clamped around it and hanging
downward. Firecoat the ring, flux the seams and place pieces of hard solder on the outside of the shank on each side, making contact with both the stock and the shank.
Turn on the torch and adjust the flame to a neutral-to-oxidizing shape with a bright inner cone. First warm the entire piece to avoid shocking the diamonds. Heat the areas around the seams and then focus the torch where you want the solder to flow. In this case, you will want to direct the heat at the points on the inside of the shank where the seams meet. This way the solder, which flows toward heat, will be drawn completely through the seam. After soldering, there should be curved fillets of solder at the corners of the seams. If you want to cool the piece more quickly, grab the top of the ring (near the diamonds) in a pair of tweezers and quench the sizing stock. Do not quench the diamonds. Inspect the seams to make sure the solder flowed completely through. Pickle, rinse, and dry the ring.
Hold the ring against the bench pin and use a saw to cut off the stock, leaving about O.5mm excess.
Slide the ring up the mandrel. It should still be a little too small, because excess material is still within the finger hole. At this point, you need to decide how to bring the ring to the correct size. You can either remove the ring and file or grind the inside smooth, or you can tap the back of the stock to increase the size a bit more, depending on how far the ring has to go. With the mandrel secured in a vise or in your bench top, use a planishing hammer with a slightly domed face to tap the sizing material. This will compress it, reducing the excess material on the inside, while stretching it to make the ring larger. Size it up just a bit smaller than desired.
Now it is time to clean up the excess and bring the ring to a finished surface. When cleaning up a ring, it is always best to start inside. There are a number of choices for removing the excess remaining material. Most traditional is an inside ring file (a narrow half-round file). It provides the most control by cutting slowly and with great accuracy. A faster but slightly less accurate alternative is using an abrasive grinding wheel. Always wear goggles and a dust mask when grinding and be very careful not to take away too much. Remember, this shank has no metal to spare, since it came in thin and since the exact measurement has been recorded. Next, file the new stock to match the contour of the ring, first on the inside of the shank and then on the sides and finally on the outside. Do not remove any more metal than is absolutely necessary. Finish the surfaces with successively finer grades of abrasive paper. This is followed by buffing and polishing the ring to a luster. The ring should rest on the mandrel with the leading edge at the line indicating size 51/4. Measuring the shank upon completion, you see that it is 1.3mm by 1mm. The width has become one tenth of a millimeter smaller, a loss of 7%, which is acceptable.
When Mrs. Ghirardelli sees her ring she exclaims, “It looks like new!” She slips it easily over her finger and proclaims it a perfect fit. As her payment is being processed, Mrs. Ghirardelli hums happily. She walks out of the store, reaches into her purse for one of the chocolate truffles she always carries with her, and strolls down the street in a great mood. After all, she is wearing a comfortable, nearly new ring while nibbling chocolate. Ain’t life grand!
Lapidary Journal, December 2000
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