Professional Jeweler Archive: Repairing a Box Clasp Tongue With Tack and Pulse-Arc Welding

April 2003

Professional Bench/Welding Technologies


Repairing a Box Clasp Tongue With Tack & Pulse-Arc Welding

Knowing how to tack-, fusion- and pulse-arc-weld at the bench saves time,increases quality and drives profits up for your shop and service department


This 14k yellow gold bracelet chain has a broken tongue. Non-torch pulse-arc welding is an ideal way to repair it because the process won’t anneal or soften the alloy in the mechanism. For this repair, we use the ABI Tack II and Tack III Pulse-Arc welders.

1. The tongue for the box clasp is broken at its critical springy location (A).
2. File or sand a smooth, flat joint on both sides of the broken tongue. The joint should be prepared so the tongue is angled properly for a secure fit in the box catch after it has been permanently pulse-arc welded into position.
3. Tack weld the broken tongue in place (B). The tack welder is set at 40 volts and on the high-energy setting. Use the tweezers lead to hold the bracelet and the pliers lead to hold the tongue. Then use moderately firm pressure between the two parts.
4. Depress the foot pedal once for a single pulse of energy to complete the tack weld. If the alignment is satisfactory, pulse-arc weld the joint. If you are not satisfied with the initial alignment, use moderate finger pressure to break apart the finding at the tack-weld joint. Resand the joint, position and retack.
5. For this volume and alloy of material, the Tack III Pulse-Arc welder is set on 40 volts at the high-energy setting. Start with lower voltage, perhaps at the medium-energy setting, until you find the combination of settings that works best for your situation. The welding pencil (C) is held 1mm to 2mm from the joint (D). The electrode of the welding pencil is recessed about 1mm inside the ceramic tip. Use repeated pulses of energy to complete the pulse-arc weld across the joint.
6. After the welding procedure, inspect the joint to ensure it’s complete. Test the spring and security of the joint.
7. Pulse-arc welding leaves a slightly uneven surface. Use medium and fine Foredom® ceramic rubberized abrasive wheels to even the surface and remove the darkened surface discoloration.
8. Polish, clean and prepare for delivery to the customer.
9. This repair took four minutes to complete. The tongue did not become annealed or softened and did not require extensive prefinishing, finishing and polishing.

Important: Tack and pulse-arc equipment settings will differ, based on the volume and alloy of the material you work with. Working with like materials will give you a parameter for the settings required for your application. Keep a record of settings and tasks for future reference.

For questions related to this process, contact Mark B. Mann at markbmann@aol.com.

This installment on welding technologies is sponsored by ABI, Cranston, RI. For general information about ABI equipment and procedures or for a list of distributors, call Janet Kirk at (888) 494-2663.

– by Mark B. Mann

Photographs by Mark B. Mann
©2003 Visual Communications

Copyright © 2003 by Bond Communications