I'm adding a circuit to my sub-panel, however I'm short the screws that hold the neutral wires down. Are these a special type or does any standard machine screw with the proper thread and head size work?
Thanks for any help.
The screws should be the same material as the busbar, or you could create issues with galvanic corrosion if there were moisture. I believe most of those are tin plated brass, while a common steel screw is typically zinc coated. The more significant issue is that dissimilar metals have different expansion rates when heated. Dissimilar expansion rates can cause fasteners to loosen, which you don't want in an electrical panel.
If you add the two effects together, it gets worse, as corrosion creates more resistance, which makes heat. Heat plus a fastener with a different expansion rate can cause it to loosen.