Resistance butt welding

In resistance welding, you press the parts between two electrodes and run a strong current through the contact point. The contact resistance heats the material there so much that it melts and welds the parts together. Be careful not to overdo the current, otherwise material will splatter or the electrodes will burn in. If the current is too weak, you won't weld properly and the joint won't hold. The electrodes and joint surfaces must be clean and grease-free, otherwise heat transfer will be uneven and you won't get a clean weld.