Metallics JCN164SS Nuts 5/16-18 Cap Nut SS (Jar 100)

Yes. The JCN164SS is a 5/16-18 cap nut, 18 threads per inch, so it threads onto standard 5/16 inch UNC coarse-thread bolts and rod. If your fastener is 5/16-24 fine thread it will not engage, and you need the fine-pitch version instead.

It is 18-8 stainless steel, the austenitic 300-series grade used for general corrosion resistance, so it holds up in damp and outdoor service far better than a plated steel acorn nut. For chloride-heavy coastal or pool-chemical exposure, 316 is the step up.

No. The JCN164SS is not Buy American compliant and is not ARRA compliant, with multiple countries of origin. If your contract carries a domestic-content clause, this part will not satisfy it.

A cap nut (also called an acorn nut) has a closed dome, so it covers the exposed end of a threaded bolt or rod. On strut hangers, equipment mounts, and panel standoffs it keeps sharp thread ends from cutting hands or snagging cable, and it finishes the end neatly. Metallics lists this one for electrical, plumbing, heating and air conditioning work.

They ship as a jar of 100, and 100 pieces is the order minimum, so the jar is the smallest unit. The jar itself weighs 2.18 lbs. Metallics does make other sizes and quantities available by request.

Treat it as a finishing nut, not a structural one. The dome is closed, so thread engagement stops at the top of the cap and the bolt cannot run through. Where you need full engagement or a torqued structural connection, use a standard 5/16-18 hex nut and add the cap nut only where a thread end is left exposed.

Mixing 18-8 stainless hardware with galvanized or zinc-plated steel sets up a galvanic pair, and the zinc coating is the one that sacrifices. In dry indoor service it is a non-issue; in wet or outdoor locations, matching the nut to the bolt material, or using a plated acorn nut on plated rod, avoids the problem.