Professional Jeweler Archive: Prong Setting Baguettes

October 2000

For Your Staff/Defining Quality

Prong Setting Baguettes

Knowing how to set baguette stones demonstrates another aspect of quality in your shop

Baguettes are among the most difficult stone cuts for bench jewelers to learn to set properly. Gone are the proportions and precise angles that define diamond cutting. Baguettes, like people, are unique individuals: some long and trim, others squat and thick. It’s their unique shapes – which never seem to match the cutting angles or the bur – that make baguettes so difficult to set. This installment of “Defining Quality” and “The JA Professional’s Guide to Fine Jewelry Craftsmanship” (p. 144) discusses prong-set baguettes and describes the features that help you determine a professional setting job.

Prong-Set Baguettes

Baguettes are most often held in place by a single prong at either end. In lesser-quality mountings, the prongs are thin, leaving the corners of the baguettes exposed and vulnerable to damage. Inexpensive mountings also use lightweight wires to support the stones. Thin prongs and weak supports limit our ability to produce a quality setting job.
Meanwhile, higher-quality mountings have prongs that span the full breadth of the stone and protect the baguette from chipping. Deeper and thicker side supports help you make cutting adjustments for deep stones and still provide your customers with a quality piece of jewelry.

Baguette Prong Setting Steps
1. Choose the correct size baguette to fit the mounting.

The baguette should overlap the prongs at both ends by a third of the prong’s diameter. The width of the baguette should fit the width of the cup without extending over the sides or being significantly narrower than the cup. When possible, choose baguettes that aren’t overly deep and have good crown angles.

Tip: Having extras to choose from will help you get the best-fitting baguettes for your mounting. Most cutters will accommodate you if they receive your request for extra baguettes at the time of ordering and if you return unused ones in good condition within a reasonable time.
2. Prepare the seat for your baguette. Because baguettes are rarely cut to ideal proportions, you’ll have to customize each seat.

Place all the baguettes on a hard, flat surface with tables down and compare their overall crown heights. Ideally, the crown heights will match and the tables will be level. If not, you’ll have to adjust the heights of the seats when setting the stones.

To begin your seat, cut a groove across the inside of the prong at the depth you want the stone’s girdle to sit. An 8/0 saw blade works well. The groove should be cut about 30% into the prong’s width.
Many baguette setters – myself included – use a narrow, flat, beveled graver to remove the metal from the prong seat. The total amount of metal you remove should not be less than 40% or more than 50%. A precise fit is most important.
If you prefer a bur to a graver, the bur must be small and undersized. I like to use ball burs as small as one-half millimeter in diameter for this operation. Larger burs can gouge the sides of your support cup, creating a seat that’s much too large for the stone.

Use a flat-bottom graver or a small ball bur to trim and angle the inside walls of the side supports. This allows the stone’s pavilion to rest evenly in the seat. Remember, you’ll also have to square up the corners for the stone to seat properly.

3. Set the baguette.

Because the prongs that hold baguettes usually are very short and often stout, I generally use a hammer tool to tap the prong over the baguette rather than bend it with pliers. First, partially bend one side down with the setting hammer. Next, partially bend the other side. Check to ensure the stone is level, is at the same height as the other stones and fits precisely. Repeat these steps until the prongs have been fully bent over the stone on each side.

4. Finish by filing, polishing and cleaning. The prong styles on each stone and each side of each stone must match.

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

© 2000 Jewelers of America Inc.
This information is required for the second level of the
JA® Certified Bench Jeweler™ program.

Illustrations by Lainie Mann – Visual Communications

The JA® Professional’s Guide to
Fine Jewelry Craftsmanship
Prong Setting Baguettes

A. Each baguette is level, tight and secure.

B. From the side, the seat conforms to the baguette proportions.

C. From a top view, the baguette’s outside dimensions cover the cup immediately below it.

D. The top of the cup is beveled, not flat.

E. When multiple baguettes are set together, their tables are at the same height and angle.

F. Prong contact is 20%-30% of the crown; prong shapes match.

G. There is no damage to the stone.

Potential Problems to Watch Out For

Stone Angled in its Seat

This stone has been set on an angle and isn’t level. Notice the girdle is uneven compared to the cup immediately below it.

Damaged Stone

A baguette can be chipped easily if it’s not set properly, even if it’s as hard as a diamond.

Incorrect Prong Contact with Seat

This seat was not created carefully. One side of the seat has insufficient prong contact; on the other, the prong isn’t in full contact with the crown of the stone.

Loose Stone

This baguette is too short for the mounting and seat. During normal wear, it will loosen and may be lost.

–by Mark B. Mann, Director of Professional Certification, Jewelers of America

Copyright © 2001 by Bond Communications