Professional Jeweler Archive: Replacing Prongs Using Tack & Pulse-Arc Welding

March 2003

Professional Bench/Welding Technologies


Replacing Prongs Using Tack & Pulse-Arc Welding

Knowing how to tack-, fusion- and pulse-arc-weld at the bench saves time, increases quality and drives up profits for your shop department. We demonstrate with an emerald ring


This 14k yellow gold, emerald and diamond ring has a broken prong that must be replaced. Steece Hermanson will replace the prong and reset the displaced emerald without unmounting any other gems. For this, he uses the ABI Tack II and Tack III Pulse-Arc Welders.

1. The prong was broken just above gallery wire (A). Hermanson uses files and a cut-off wheel to remove the prong below the gallery wire. The cut-off wheel also leaves an indentation for use with the new prong in the next step.
2. He selects a cylinder square bur (B) the same diameter as the new prong (C) and creates an indentation in the side of the gallery wire and ring for a new 14k yellow prong.
3. Using his Tack II tack welder with the pliers (D) and ring clamp leads (E), Hermanson tack-welds the new prong (F) in place. He sets the Tack II tack welder to 45 volts on the low-energy setting. The joint is clean and free of metal fragments. He applies moderately firm pressure between the two surfaces and depresses the foot pedal to complete the weld and temporarily hold the new prong wire to the ring.
4. The weld pencil for the Tack III Pulse-Arc Welder contains a #2 diameter electrode covered by a #2 diameter ceramic tip. He removes the ceramic tip (top) by loosening the set screw (G) and replaces it with one he modified for prong work (bottom). The electrode is recessed into the ceramic tip about 1/2mm to 3/4mm.
5. Using the weld pencil and pliers lead, Hermanson pulse-arc welds the joint of the new prong and the ring at the bottom (H). Because it’s already tack-welded, pulse-arc welding will finish the welding process. After pulse-arc welding the joint, he inspects the overall joint to ensure it’s properly aligned.
6. To pulse-arc weld the prong onto the ring, he sets his Tack III welder on the high-energy setting and 35 volts. He pulse-arc welds the sides of the prong. Each depression of the foot pedal elicits a brief surge of electrical amperage/voltage discharged through the electrode to complete a small weld hit. The job requires several weld hits on each side of the prong.
7. He pulse-arc welds the new prong at the joint of the top of the gallery wire and the prong face. He inspects the newly welded prong, adjacent stones and overall condition and determines some fill is needed in a few locations.
8. He uses 29 gauge 14k yellow gold wire (J) to fill voids around the prong (I). Using the same welder settings, he places the wire tip over the void, the electrode over the wire and welds to fill the void.
9. After he completes welding the new prong in place, he uses a small brass wire wheel brush on his flexible shaft to remove the carbon residue (surface darkening) caused by the welding process.
10. He inspects the complete joint for openings or other imperfections and ensures a good strong seam. Notice the adjacent stones are unaffected by the tack- and pulse-arc welding process.
11. All that’s left are minor prefinishing, resetting the loose stone and a bit of final polishing.
12. The new prong is shown by the arrow (K). From start to finish, the project took 25 minutes and didn’t require unmounting other gems.

Direct questions to Steece Hermanson at shermanson@ftc-i.net or Mark B. Mann at markbmann@aol.com.This installment is sponsored by ABI, Cranston, RI. For information on ABI equipment and procedures or for a list of distributors, call Janet Kirk at (888) 494-2663.

– by Mark B. Mann

Technical contributions by JA® Certified Master Steece Hermanson of Galloway & Moseley, Sumter, SC

Photographs by Mark B. Mann
© 2003 Visual Communications

Copyright © 2003 by Bond Communications