Professional Jeweler Archive: Fabricating a Three-Stone Ring

December 2000

For Your Staff/Defining Quality


Fabricating a Three-Stone Ring

The first part of this three-part series discusses the center-stone platinum prong assembly

– by Tom Weishaar, Master Bench Jeweler and Shop Manager, Underwood's Fine Jewelry, Fayetteville, AR


With the current popularity of three-stone rings, this is a good time to review how they are made. This first of three articles on fabricating a platinum and gold three-stone ring focuses on the platinum prong assembly for the center stone.


Steps to Fabricate the Center-Stone Platinum Prong Assembly

1. The center stone measures about 14mm by 10mm. Use 1.2mm-1.3mm diameter round wire for this assembly. The total length of wire required is 140mm. We selected an alloy of 10% iridium/platinum wire. Here’s how to estimate the overall length of the wire required:

Prongs: About 12mm each. This leaves 3mm-4mm to place into the solder board for assembly. See below.

Upper gallery wire: About 38mm. To calculate the length of the wire required, measure the stone and follow this formula: 1/2 the length + 1/2 the width x 3.1416.

Lower gallery wire: About 32mm. The lower gallery must be smaller than the upper gallery.

2. Form the upper gallery wire into an oval, exactly matching the shape of the stone but with an outside dimension slightly smaller.
The outside dimension of the upper gallery wire should be slightly smaller than the outside dimension of the stone. The shape of the stone and the shape of the wire formation should match exactly.
3. Form the lower gallery wire slightly smaller than the upper gallery wire. The difference in size dictates the prong angle, which for this project is 65° to 70°.
Keep in mind the overall prong angle when you fabricate the lower gallery wire.
4. Place the formed and soldered lower gallery wire in a shank-forming block and gently shape it to the expected radius of the ring shank.
The lower gallery wire is in the shank-forming block.
5. Prepare the prongs. The usual recommendation is the prongs should be twice as long as the depth of the stone. Don’t cut the prongs shorter! Prong wires are not the place to save money on the cost of metal.

6. Measure and scribe where you will solder the prongs. At each scribe line, bur a notch at a slight angle and with a depth of one-third the overall wire dimension. By increasing the amount of surface contact between the gallery wires and the prongs, the notches increase the overall strength of the assembly. Also this type of joint is more aesthetically pleasing.

Carefully measure and mark each prong location. Cut the notches with a cylinder bur of the same diameter as the prong wires.
7. Holding and joining the assembly during soldering is critical. One method that works very well is to use a high-heat ceramic soldering block and a special prong- angle measuring tool. Mark the ceramic block with the center point of the lower gallery wire. Using a fine point marker, draw six lines radiating from the center point past the marks you made indicating the prong locations.
Press the lower gallery wire into the ceramic block, then use a sharp tool to mark the prong notch locations into the ceramic block.
Bench Trick: Write “Platinum” on one top edge of the ceramic board and “Gold” on the other so you can use the same block for both metals.
8. Remove the lower gallery wire from the block and, for each prong, drill a 3mm deep hole at the angle indicated by the prong-angle tool.
Align the leading edge of the prong angle tool with a prong indicator on the soldering block. For each prong, drill a hole at the angle indicated by the prong-angle tool.
Bench Trick: To align prongs, Steece Hermanson, JA® Certified Master Bench Jeweler,™ developed protractor-type devices. Each is a small sheet of metal cut to a particular angle, with that angle (65°, for example) engraved on the surface for reference. For this project, we use the 70° angle tool.
9. Place the lower gallery wire back into position on the block and push the prong wires into the drilled holes. The prongs should fit snugly into the notches. Use 1,700° or 1,600° platinum solder to join the prongs to the lower gallery wire.
Ready for soldering.
10. Place the upper gallery wire into the prong assembly. You can adjust its height and alignment by gently changing the angles of the prongs. After you’ve made all the alignment and height adjustments, solder the upper gallery wire in place.
Ensure proper alignment.
11. Remove the prong assembly from the soldering block and finish and polish it.

The next installment of this series will feature the assemblies of the baguette wires.




The JA® Professional's Guide to Fine Jewelry Craftsmanship

Fabricating a Three-Stone Ring

By Mark B. Mann
Director of Professional Certification
Jewelers of America


Professionally Fabricated Prong Assembly for a Center Stone

A. The upper and lower gallery wires are evenly spaced and proportionate.

B. The upper and lower wires have the same outside dimensional shape.

C. The space between the upper and lower gallery wires is deep enough so the culet of the center stone won’t be below the level of the bottom gallery wire.

D. Notches (into which the prongs will be soldered) are burred into the gallery wires at a depth of one-third the wire’s diameter.

E. There is no excess solder at any solder joint nor any cold or incomplete solder joint.

F. Prongs are perpendicular and evenly spaced.

G. Prongs are long enough for stones to be set into them.

H. Prong angles are consistent from prong to prong: 65° to 70° for this project.

I. There are no tool marks on the prong assembly.

Potential Problems to Watch for
The upper gallery wire should not be visible from the top view once the stone is set.
The prong angle should accommodate the stone’s proportions. These prong angles are too straight and the prongs are spaced unevenly.
No notches were burred into the upper or lower gallery wires for the prongs to be soldered into, resulting in sloppy and weak solder joints.
Excess solder and excessive tool marks are visible in the solder joints – signs of errors in workmanship.
© 2000 Jewelers of America Inc.
This information is required for the fourth level of the JA® Certified Bench Jeweler™ program.

For information about the JA® Certified Bench Jeweler™ program, call JA at (800) 223-0673 or visit www.jewelers.org.

Illustrations by Lainie Mann – Visual Communications
JA Masters in Motion will be conducted in February during the Rio Grande Catalog in Motion at the Tucson East Hilton, Tucson, AZ. Three JA Certified Master Bench Jewelers will present four 90-minute demonstrations each day Feb. 2-4. The presentations will be played live via close-up video cameras and large-screen monitors. The sessions are interactive. There is no cost for admission and seating is on a first-come, first-seated basis. Call JA at (800) 223-0673 for information.

Copyright © 2001 by Bond Communications