December 2002

Professional Bench/Defining Quality

Setting Round Brilliants in Shared Prongs

Knowing how to professionally set round brilliant-cut stones in a ring mounting with common or shared prongs demonstrates another aspect of quality in your shop

Setting dia-monds or colored gemstones in ring mountings that have common or shared prongs is a popular choice for customers who like a strip of color and brilliance with little or no space between the stones.

Inspection of Gemstones and Preparation for Setting

For this project Steece Hermanson of Galloway & Moseley, Sumter, SC, will set five diamonds measuring about 3.8mm each and totaling about 1 carat. Hes resetting customer diamonds that vary slightly in overall make, have diameters that measure within 1/10th of each other and have minor differences in depth. When finished, he wants all diamond tables set at the same height. Here are the steps he uses for inspection and preparation:

1. He places the diamonds table-down in a row over a smooth, flat surface and arranges them in order of total depth, with the shallowest at one end.

2. He measures the diameters in two or three locations to ensure they are round.

3. After arranging the diamonds, he inspects the mounting. This ring is 14k yellow and white gold with 14k white gold prongs. He makes sure each prong is positioned properly and aligned symmetrically.

4. Next he checks the accuracy of the ring size and prefinishes the ring.

Bearing Creation Procedure

Hermanson selects a setting bur that is equal to or slightly smaller than the diameter of the diamonds.

5. He starts by creating the bearing at the center location for the diamond with the largest diameter and overall depth. For the 14k mounting, he uses a less aggressive setting bur made of vanadium steel.
6. The bur is equally in contact with all four prongs. Hermanson doesnt remove more than 25% of the thickness from any prong. When he places the diamond in its potential bearing, the height of the prong in relation to the table is 110%-120%.

7. He selects the next largest diamond and prepares the bearing for it using the same methods. Hes careful not to remove too much metal and prefers the bearing to be as tight as possible.

8. He repeats the procedure for each bearing, making adjustments for differing diameters by drifting with the bur. For diamonds with lower crown heights, he leaves the bearing slightly higher.

9. Next he removes all flashes and rags of metal created by burring the bearings. To ensure the diamonds will be level, at the same height and evenly spaced when finished, he pushes each one into its bearing with a brass pusher. The table orientation of all diamonds should be consistent.

10. He completes this step of the procedure by making necessary adjustments so all prongs are of equal height.

11. He uses a cup bur to fashion each prong top and performs additional finish work on the mounting and prongs.

Seating and Setting the Diamonds

Now Hermanson must seat and set each diamond.

12. He starts by placing the diamonds in their bearings carefully matching each one to its proper location.

13. Using chain-nose pliers, he partially bends each prong to initially secure each diamond in its bearing using the following sequence:

14. Next he inspects the work to make sure each diamond is level and even.

15. He finishes by bending each prong over the diamond, being careful not to bend prongs too far in a single movement because one prong secures two diamonds.

16. Finally he inspects with a 10X loupe to be sure there is full contact between the diamond and each prong and that no prongs are left standing upright.

Procedure Summary

Setting five round brilliant diamonds in common prongs and finishing the ring mounting required 35 minutes.

For questions related to this process, contact Steece Hermanson at shermanson@FTC-I.NET.

By Mark B. Mann

Technical contributions by JA® Certified Master Bench Jeweler Steece Hermanson
shop manager for Galloway & Moseley, Sumter, SC

Illustrations by Lainie Mann
© 2002 Visual Communications
(406) 961-4426

Setting Round Brilliants Using Shared Prongs

Professional Setting of Round Brilliants in Shared Prongs

A. The diamonds are equally spaced and the tables are level and even. There is no variation in the overall height.

B. The orientation of every diamonds table is consistent (important for diamonds 0.20 carat and above).

C. All prongs are evenly spaced and identically fashioned, and they secure each diamond.

D. The overall prong length when finished is equal to the height of the table.

E. No more than 50% of the overall prong thickness was removed.

F. There are no rags of metal or flashing evident from the burring procedure.

G. No diamonds are in contact with one another, and no diamonds are damaged.

H. All tool marks have been removed, and the overall polish is smooth and even.

Potential Problems to Watch for

The diamonds are set at differing heights and are not level or even.
More than 50% of the prong thickness has been removed. The prong will catch and pull back, and the diamond can be lost.
The space between the diamonds differs, and the tables are not level.
The diamonds are set too low. The prongs are unevenly fashioned and have been left too long, burying the diamonds in the mounting.

By Mark B. Mann

Illustrations by Lainie Mann
©2000 Visual Communications
(406) 961-4426

This series is sponsored in part by Jewelers of America, (212) 768-8777

Copyright © 2002 by Bond Communications