Professional Jeweler Archive: Fabrication of a Wire Prong Assembly for Pear-Shaped Gemstones

March 2002

Professional Bench/Defining Quality


Fabrication of a Wire Prong Assembly for Pear-Shaped Gemstones

Knowing how to accomplish this task demonstrates another aspect of quality in your shop


This month we build on last month’s installment of Defining Quality/Fine Jewelry Craftsmanship (February 2002, p. 89-93), which covered fabrication of a prong assembly for a round gemstone to be set in stud earrings. The variations of prong assemblies are virtually endless, and this month we feature one for a pear-shaped gemstone to be used as a pendant.

Cast versions are readily available, but a well-crafted, handmade prong assembly is stronger and more detailed. Prongs also can be handmade to fit non-standard gem shapes.

Upper Gallery Wire

The upper gallery (A) is made from 1.35mm round wire. It should have an outside dimension slightly smaller than the gemstone’s outside dimension and mimic its shape. When the stone is set, the upper gallery should not be visible from the top.

Lower Gallery Wire

The lower gallery (B) is made from 1.35mm round wire. It should have an outside dimension smaller than the upper gallery. The size difference between the two dictate the angle of the prongs – generally preferred to be about 70&Mac251; to 80.&Mac251;

Prongs

This prong assembly will have two 1.35mm round wire prongs (C) and one V-shaped point prong fashioned from 1mm by 3mm flat wire (D).

Making the Gallery Wires

  • For a pear-shaped gem measuring 17mm by 10mm, the gallery wires must be shaped carefully by hand to fit the profile of the gem.
  • After the gallery wires are formed, solder the open joints using hard solder.

Laying Out the Prongs and Notching the Galleries

  • Using dividers, measure the prong locations for the upper gallery from the centerline. You also could use graph paper as an aid for symmetry.
  • At each mark, make a saw cut to a depth of about one-third the wire thickness.

  • Widen the saw cuts with a 3-square file and finish them with a round file so the prong wire will fit snugly into the rounded notch. The notch should be about one-half the depth of the wire and should be at a slight angle to accommodate the taper of the setting.

  • Place the lower gallery inside the upper gallery and mark the prong locations.
  • Notch the prong locations for the lower gallery wire.
  • All components should be prepolished before assembly.

Assembling the Components

The most common approach to assembling the pieces is to first solder the prongs to the lower gallery wire, adjust prong angles as necessary, fit the upper gallery and then solder it in place. Following are a few methods to accomplish this:

U-Shaped Wire Method
  • Bend wire into a U shape to form the two opposing prongs.
  • Fit the U shape into the lower gallery and solder with medium solder.
  • Remove by sawing or cutting the U portion at the bottom.
Charcoal Block Method
  • Prepare the two back prongs 3mm- 4mm longer than needed.
  • Make the V front prong by cutting a length of 3mm by 1mm wire.
  • Notch down the center portion of the wire with a hart bur. The depth of the notch should be 90% of the wire thickness.
  • Fold into a V shape at the notched portion and solder the joint with medium solder.
  • Position the lower gallery on a charcoal block.
  • Lightly push all three prongs into the block at each prong location and solder with medium solder.

Final Steps

  • After you’ve soldered all prongs to the lower gallery, make final adjustments to fit the upper gallery, which you then solder in place with easy solder.
  • General cleanup and polishing is all that’s needed before the addition of the bail and any embellishments.

By Mark B. Mann, Director of Trade Programs, Jewelers of America

Technical Content by Wayne Lenkeit, JA® Certified Master Bench Jeweler,™ Lenkeit Manufacturing, Temecula, CA

© 2002 Jewelers of America
Illustrations by Lainie Mann – Visual Communications

This information is required for the third level of the JA® Bench Jeweler Certification™ program.


The JA® Professional’s Guide to Fine Jewelry Craftsmanship

Fabricating a Wire Prong Assembly for Pear-Shaped Gems

By Mark B. Mann, Director of Trade programs, Jewelers of America

 

Professionally Hand-Fabricated Prong Assembly
for a Pear-Shaped Gemstone

A. The solder joints are complete, clean and free of visible excess solder, pits and cracks.

B. The prongs are symmetrical and evenly spaced.

C. The upper and lower gallery wires are evenly spaced.

D. The upper and lower gallery wires are notched, and the prongs are evenly spaced and soldered into them.

E. The finish is even, smooth and free of tool marks.

F. When you view the piece from the top, there is no visible metal with the exception of the prongs.

G. No portion of the gemstone is in contact with the upper gallery wire.

Potential Problems to Watch for

This prong assembly was poorly made; gallery wires and prongs are soldered unevenly and lack structural strength to secure the gemstone.
The wire diameter selected for this pendant was too small; through normal wear, the prongs could become deformed, and the gemstone could be loosened and ultimately lost.
This prong assembly was fabricated with little attention to detail; the shape of the gemstone and prong assembly don’t match.
The upper gallery wire is too large for the gemstone.

This information is required for third level of the JA® Bench Jeweler Certification™ program.

For additional information about bench jeweler certification, call Jewelers of America at (800) 223-0673 or visit www.jewelers.org.

Copyright © 2002 by Bond Communications