Ask a seasoned bench jeweler how many rings he or she has sized and they’ll probably give you a figure in the quadruple digits.
The following is a compilation of tips and tricks to help you perform this mundane task better and faster.
Using a Butt Joint
The most common joint used in the sizing of rings is a butt joint. When executed properly, it provides a seamless finish, leaving no evidence that the ring was ever sized. The basic steps of this process include cutting through the bottom center of the shank and either removing metal (to size down) or adding sizing stock of the appropriate length (to size up). Tips for performing this process accurately, as demonstrated in the MJSA Press book At the Bench by Gregg Todd and Greg Gilman, include:
|Use sizing stock that is slightly wider and thicker than the shank — about 0.2 mm wider and 0.1 mm thicker will do.|
|After measuring the stock with dividers, saw along the outside edge of the scribed line to ensure that the piece being added is the correct length.|
|When you slide the ring up the mandrel to the desired stock and insert the sizing stock, the joints should fit precisely. If they don’t, fit one side of the joint precisely by gently sawing through the cut again, using the saw blade as a file.|
|After firecoating the ring and fluxing the joint, apply hard solder and flow one joint. Then you can bend and adjust the other joint into position more accurately.|
|Once the butt joint is soldered in place and has been filed, sanded, and smoothed, slide it onto the mandrel and round it out with a non-marring mallet. Double check to make sure the size is correct. To avoid tapering the interior surface of the shank, reverse the ring on the mandrel and repeat this step. (Note: This step should be done when sizing any ring, regardless of the type of joint used.)|
Using a Dovetail Joint
While dovetail joints take longer than butt joints, they offer an additional measure of support to a sizing. There are two types of dovetails generally used: V-notched and rounded. In this procedure, a V-shaped groove is filed on each side of the shank (V-notched), or the shank is cut open to the desired size and rounded at each end with a barrette needle file (rounded). A corresponding piece of sizing stock is then cut and grooved accordingly, fit, and soldered into place. Tips for performing this process accurately, as demonstrated in the MJSA Press book At the Bench, include:
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|When filing a V-shaped groove into the shank, use a square needle fire and work on the inside of the shank first. This provides greater stability and a better cut.|
|Make sure the V-shaped groove in the sizing stock is equal to half its thickness. (For example, if the sizing stock is 1.5 mm thick, saw to a depth of 0.75 mm.)|
|If after inserting the grooved plug into the shank you find that it doesn’t fit well, true the joint by gently sawing through the V-shaped cut, using the saw blade as a file to reshape the cut.|
Just as with traditional soldering, you can use either a butt joint or a V-notched joint when sizing a ring using a laser welder. The key here is using the correct voltage, time, and beam diameter on your laser welder. "If you use too small of a beam diameter for the core weld when sizing a ring, it will often result in pitting or holes," says Giles Pope, director of education for LaserStar Technologies in Riverside, Rhode Island. "The jeweler should increase voltage, milliseconds, and beam diameter to enable the weld to penetrate at least 51 percent to the core of the ring being welded. If the welder being used cannot achieve 51 percent penetration with a butt joint only, the jeweler can use a V-notched joint and backfill, followed by an overlapping core weld." In an overlapping core weld, the laser shots create flat metal puddles along the surface.
Once the core weld is in place, Pope advises the jeweler to readjust the laser welder’s total parameters (voltage, time, beam diameter, hertz rate) to lay the filler wire with a hammering and smoothing process. "If the beam diameter is not widened for filling and smoothing, the laser energy will be too strong and consequently splash the alloy around, resulting in an insufficient weld."
The following is an excerpt from "The Ultimate Repair Guide" that appeared in the June 2011 issue of MJSA Journal, which also featured sections on retipping and chain and findings repair. To order a copy of the complete guide, contact MJSA at 1-800-444-6572, ext. 3038.