"Brian Elfert" wrote in message
It sounds like 18-8 is probably the common grade found in hardware stores.



I am buying some socket cap screws. The black oxide ones will rust even
in just a single light rainfall. I am building something that may
occasionally get used in the rain.

Brian Elfert

We use the 18-8 machine screws and socket cap screws, mostly from McMaster.
They are used in tooling that is subjected to steam, water (pH 6.4), air,
vacuum cycles every 30 to 60 seconds for 24 hours a day, sometimes for
months at a time. They hold up well. Never found a reason to use a more
expensive item.
Ed