Professional Jeweler Archive: Prong Setting Round Brilliants Using Foredom's AllSet Quick-Change Adapter Kits

June 2004

Professional Bench/Manufacturing Up Close


Prong Setting Round Brilliants Using Foredom's AllSet Quick-Change Adapter Kits

Knowing these tips and techniques contributes to higher levels of proficiency for your shop


We covered one popular method of setting a round brilliant gemstone in prongs on pages 95-97. Bench jewelers we surveyed report another popular method: Using a 90&Mac251; low-speed bearing bur to cut a bearing one prong at a time because of a gem’s size, proportions or other features. For this example we will use a 90&Mac251; low-speed bur on individual prongs at a controlled height and depth using a Foredom #52 Quick Change Handpiece and the Foredom AllSet #52 Quick Change Adapter Kit. The easy-cut prong guide offers systematic controls to cut prongs at higher proficiency rates.

1. Set a 6.5mm round brilliant gem in a Hoover & Strong solitaire. Select a 90&Mac251; low-speed bearing bur measuring 2.7mm to create notches in individual prongs for the bearing. Remove all tool marks and make sure the prong angles are the same and evenly spaced.
2. To prepare the Foredom #52 handpiece for the Foredom AllSet attachment, loosen the nose cone of the handpiece with a wrench and remove it.
3. The nose cone is replaced with the stainless steel one from the #52 Foredom AllSet Adapter Kit. The table-guide screws into it.
4. Adjust the easy cut prong guide (A) and prong stop (B). The prong guide will support the prong being burred and seldom requires adjustment from job to job. The prong stop is set for the depth of the cut. Use of the prong stop is optional. My goal is to remove about 33% of the prong’s total depth.
5. The prongs are sanded flat on top using 400-grit abrasive film on a flat disc.
6. Insert the bur into the handpiece and adjust the cutting height. Place the ring prongs down on the table guide. The prong to be cut is positioned next to the prong guide (C). The opposing prong is positioned against the prong stop (D). Lubricate the bearing bur with bur lubricant and begin to make a cut in the prong by sliding the setting along the prong guides (E). Foredom’s series TX Flex Shaft provides full torque at low to medium speeds.
7. While sliding the setting, the prong being cut (F) is supported by the prong guide, which prevents the bur from wrapping around it through the cutting process. The prong stop (G) simultaneously controls the depth of the cut in each prong. This feature is ideal for multiple settings of the same style or when the ultimate precision is mandatory.
8. Inspect the ring to ensure the bearing in each prong is cut equally. Remove the flashes or rags of metal created by the burring process using a flat-bottom graver. Place the gemstone in the bearing and check that:
  • The overall depth of the bearing cut and the height of the gemstone are appropriate.
  • The gemstone is level.
  • There are no gaps or other irregularities between the bearing and the gemstone.
9. Bend the prongs over the gemstone by bending opposing prongs (below, left).

Important: Check to make sure the prongs and crown of the gemstone are in full contact. Make necessary adjustments if not. After the prongs are bent, Michael Dickey advises using parallel pliers to further secure the gem. His technique is to gently squeeze adjacent prongs together. He follows the steps outlined in the diagram.

10. Shape the prongs using a cup bur and file, ensuring even and consistent form. For polishing and finishing, I use a short bristle brush with Foredom’s Platinum Blue compound. After cleaning, I finish with Foredom’s Platinum White compound and a cotton buff. It is 8000-grit and applies a professional luster.
11. The prongs’ contact on the crown is about 30%. The top of the prongs are close to or slightly below the height of the table when viewed from the side
Dickey changed his procedure for setting round brilliants in prongs to using the Foredom AllSet and burring individual prongs. “I’ve reduced potential prong failure, improved setting quality and increased our shop’s proficiency.” he says. “With the prong guides, it’s hard to have a setting go wrong.”

Foredom makes the AllSet Quick Change Adapter Kits for its No. 52 (shown in this article), No. 10 and No. 18 quick-change type handpieces. Kits include a selection of setting guides primarily for prong and channel setting. I found the components quick to assemble, professionally designed and manufactured, and easy to use.

This installment was sponsored by Foredom, Bethel, CT. For information on Foredom tools, equipment and accessories or for a list of distributors, contact Michael Zagielski at (203) 792-8622 or sales@foredom.com.

The solitaire featured in this article was provided by Hoover & Strong, Richmond, VA.; (804) 794-3700.

Technical contributions by Michael Dickey of Michael Dickey Designs, Redlands, CA; (909) 335-9919, michael.dickey@verizon.net. Dickey is a 25-year veteran at the bench and a JA Certified Master Bench Jeweler. He operates a national trade shop performing repair, custom order, CAD CAM and laser-welding services for retailers.

– by Mark B. Mann

Technical Contributions by Michael Dickey of Michael Dickey Designs, Redlands, CA

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Photographs by Mark B. Mann

© 2004 Visual Communications Inc.

Copyright © 2004 by Bond Communications