Today I Learned
While searching for longer M5 button head screws (to attach my Thor seat to the S40), I was given the choice of 18-8 stainless vs. 316 stainless. Must do research. Here's what I found:
"18-8 stainless steel, also sometimes called 304 stainless, is the most common type used for fasteners. It contains 18% chromium and 8% nickel and features strong corrosion resistance, but is softer, and thus weaker, than some other grades such as 410 stainless. Self-drilling screws are available in 18-8, but are generally recommended only when drilling into wood or soft materials.
303 stainless steel is similar to 18-8 stainless, but has a larger sulfur content, making it one of the more machinable stainless steel grades. This machinability has made it very popular in the fastener industry, particularly in the manufacture of spacers and standoffs.
316 stainless steel is both hardened and extremely corrosion resistant, making it a good choice for larger nuts, bolts, and washers used in harsh environments, such as coastlines.
410 stainless steel is a hardened type common in some fastener lines, especially self drilling screws. The hardening allows for more strength and stability, especially when being installed into metal materials."
I ordered some 316 bolts & lock nuts from McMaster-Carr.