I work as a maintenance technician and part of my work involves the repair and upkeep of systems in a chemical plant. Naturally this involves working with stainless fittings and fasteners.
Usually an imperfection in a mild steel thread won’t prevent you from doing it all the way up. Given enough force, a nut will slide over a damaged thread and you can continue working. Not so with SS fittings. A damaged thread will need to be repaired before you can send a nut home or you risk jamming it in place, unable to back it off.
My team and I were having a discussion about why this is, and what was going on at the molecular level to cause the difference.
The best we could come up with was either:
A) The superior tensile strength of Stainless Steel causes the fitting to jam, rather than deflect under loading, or;
B) The graphite content in mild steel acts as a dry lubricant, making the fasteners more forgiving of imperfections.
Or a combination of both. Can anyone shed some light on this?