Spot Welding

Questions and Answers

On all welders the tongs should mate at the weld surface when the electrodes are attached. Altering the bend without or with heat might be a solution. Keep in mind the heat may anneal the tongs and reduce their strength. Good quality equipment has adjustments for alignment.

This is a machinery design/warranty issue not a resistance welding issue. It is not in the scope of this blog.

Many components in a resistance welding machine should see 4-6 L per minute (1-1.5 gal/min) of water. This is a very high necessary flow of cool water. The specifications for this water can be found in:

AWS Specification AWS J1.2 Guide to Installation and Maintenance of Resistance Welding Machines

Proper sizing of the electric, air and water for a welder installation is very important. It should be done by professionals. The machine manufacturer may provide specifications for the installation. Contact local qualified installers.

This subject is beyond the scope of the blog.

  Water Manifold

Reference: American Welding Society - AWS J1.2 Guide to Installation and Maintenance of Resistance Welding Machines

An inquiry came in after reading about PCT, It asked when does current flow? To clarify current flows during weld time. Be it AC, DC or MFDC equipment.  Weld time is when the current is ON. The current is on the length of time T of PCT. The amplitude of the current is C of PCT. By now you know that the pressure or force is P of PCT.

  Spot Weld Schematic

To see and understand this better please view another article in this blog:


Reference: RWMA Resistance Welding Manual 4th Edition

The answer is yes. One could, but it is not recommended. Stainless requires relatively high forces and pure copper without alloy strengthening additives does not have the strength at the temperature generated to hold up. Mushrooming will occur quickly. Weld nugget failure will be frequent and require constant electrode dressing and attention.

My answer is no don’t use pure copper. In another blog article electrode selection for stainless steel was addressed:


Stainless Steel weld schedules are available in:
AWS Specification C1.1 Recommended Practices for Resistance Welding
In this specification the data necessary to dial in a good starting weld schedule is available

Reference: AWS Specification C1.1 Recommended Practices for Resistance Welding
                  RWMA Resistance Welding Manual 4th Edition

Job shops continue to have foot operated resistance welders in use. They are fewer but they are out there. The operators foot actually provides the initiation and force of the weld with leverage multipliers built into the machine design. To replace the persons foot a force mechanism must be provided. It must be capable of providing the force needed for the application.

 Foot Operated Rocker Arm



To spot weld 1 mm (0.040 in) or 3 mm (0.120 in) steel a force of 3 Kn (700 lb) to 4.5 Kn (1000 lb) approximately might be used. A pneumatic cylinder which could produce that strength through the mechanical advantages built into the machine would be necessary. Stroke length would also need to be considered. These and other considerations can be discussed with local area Resistance Welding Machine Suppliers or Distributors. They will know the proper sources for the parts and information to make this conversion a success.

Machine design is beyond the scope of this discussion.

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