Professional Jeweler Archive: Setting Princess-Cut Diamonds in Prongs

September 2002

Professional Bench/Defining Quality


Setting Princess-Cut Diamonds in Prongs

Knowing how to professionally set princess-cut diamonds into prongs demonstrates another aspect of quality in your shop


Setting princess-cut diamonds is a requirement at Designs in Jewelry Inc., owned and operated by Barry Pizzolato. “If not professionally set, these gems will break either when set or when worn,” cautions Pizzolato.

For this article, Pizzolato sets a 1-ct. princess-cut diamond measuring 5.5mm by 5.5mm in a 1.25-ct. classic cathedral setting for round diamonds (Series #204) from Roseco of Dallas, TX. “This is the best solitaire on the market for this style of setting because the prongs are substantial and offer the best protection for the corners of the diamond,” he says.

Inspection, Job Analysis and Preparation

Pizzolato inspects the diamond and determines it has no characteristics requiring special consideration when setting, such as a thin, wavy girdle or unevenly cut corners.

He adjusts the prongs so they’re symmetrical and ensures that each point of the diamond is positioned with the center of each prong. Notice the girdle is slightly above the top of the prong and covers 40%-50% for this step. If your diamond is slightly rectangular, adjust the prongs accordingly.

Preparing the Relief Portion of the Bearing

Pizzolato uses a fine pair of dividers to mark each prong at the level where the girdle will be seated to determine where he will cut the bearing. He selects a #7 ball bur (about 0.7mm), positions it sideways against the prong and burs a small pilot hole. He repositions it so he can bur straight into the metal so the bur doesn’t wander. The relief is cut 60% of the depth into the prong. He suggests using a new bur for each setting.

Creating the Bearing

Pizzolato selects a #5 ball bur (about 0.5mm) to hollow out the top of the pilot hole. This will allow the point of the princess cut to be suspended in the hollow area and will protect the diamond from being broken or chipped in the setting process.

Using the #5 ball bur sideways, he cuts a bearing where the diamond will be seated. It’s cut from the bottom of the pilot hole down the “throat” of the prong. The bearing cut is 0.5mm deep.

He uses a #4 three-square file to create a notch at the girdle level so the prong folds rather than crimps when bent.

Seating and Setting the Diamond

Pizzolato removes all traces of metal flashing then seats the diamond in the bearing. Before bending the prongs over the diamond, he ensures that:

  • The diamond’s pavilion angle matches the angle of the cut into the prong.
  • The cut of the bearing is slightly deeper in the central portion of the prong to accommodate the corners of the diamond.
  • There is no visible space at or slightly below the girdle.

Pizzolato positions his modified notched flat-nose pliers at the girdle position on one prong and at the top of the opposing prong. First, he slightly bends each prong over the diamond, one at a time, working opposites to initially secure them in place. Next he positions his notched pliers over the top of opposing prongs and gently rocks back and forth, bending the prongs further over the diamond. He carefully inspects each corner, ensures the diamond is level and that all prongs are equally in contact. “Constantly inspect your work through this process,” he says. He bends each prong in small increments, inspecting all the way through the process. The notch helps keep the pliers from slipping.

Finishing

Pizzolato finishes the tops of the prongs at an angle similar to the diamond’s crown angle. The prong tops are even with the diamond’s table. He ensures there are no sharp corners or flashes of metal.

Procedure Summary

Setting a princess-cut diamond in a prepolished head using this process takes Pizzolato 15 to 20 minutes for an evenly proportioned and symmetrical 1-ct. diamond.

“V” Prongs

Be sure to see next month’s Professional Jeweler featuring Pizzolato’s techniques for setting princess-cut diamonds into “V” prongs.

Barry Pizzolato began his career in 1971, working at the bench in his first retail store. Five years later, he launched Designs in Jewelry Inc., a design and manufacturing store in Metairie, LA. Pizzolato credits the success of his enterprise to design, manufacturing and repair services. He is a former member of the Jewelers of America Board of Directors, served on its education committee and reviewed the bench jeweler certification criteria. He’s now developing tools to be used widely in the jewelry industry. For questions related to this process, call him at (504) 888-0713.

The four prong heads featured in this article are from Roseco, Dallas TX; (800) 527-4490, www.roseco.com.

– by Mark B. Mann

Technical Contributions by Barry Pizzolato, owner of Designs in Jewelry Inc., Metairie, LA

Illustrations by Lainie Mann, Visual Communications, (203) 268-5265.
© 2002 Visual Communications


Prong Setting of Princess-Cut Diamonds

Professional Setting of Princess-Cut Diamonds in Prongs

A. The diamond is level and the table is even with the tops of the prongs.

B. The prongs are snug and flush against the diamond.

C. A relief hole has been created in each prong so no metal from the prong touches the point of the diamond. (Unable to view after the diamond is set.)

D. The prongs are tailored and finished.

E. There are no flashes of metal at the prong bearings.

Potential Problems to Watch for

Solder was used to fill visible gaps and tighten the diamond in the setting. The solder flowed into the relief holes. The diamond was broken during normal wear as the solder came in contact with the tip of the diamond.
There are visible gaps and the bearing is unevenly cut – a sign of errors in workmanship. The diamond will loosen and may become lost during normal wear.
The diamond prongs are unevenly finished.
Too much metal was left at the top of each prong. The ring is sharp and uncomfortable to wear. Flashes of metal were not removed where the bearings were prepared.

– by Mark B. Mann

Illustrations by Lainie Mann, Visual Communications, (203) 268-5265.
© 2002 Visual Communications

This series is sponsored in part by Jewelers of America

Copyright © 2002 by Bond Communications