A pin welder is used to?

• A. Weld insulation pins
• B. Weld steel plates
• C. Weld copper wires
• D. Weld plastic fittings

Answer: (B)

A pin welder is a resistance-welding tool used to attach fasteners, called pins, to a metal surface. In insulation work, those pins are welded into a steel plate or deck so the insulation can be held in place. The machine delivers a brief, high-current pulse that fuses the pin into the plate, creating a secure anchor without needing screws or glue. That makes welding onto the steel plate the central use of a pin welder in this context, which is why the option about welding steel plates best fits. The other tasks—welding copper wires or plastic fittings—require different tools or processes, and joining two steel plates isn’t the typical insulation-focused use of a pin welder.