Metallics JSFN3816SS Nuts 3/8-16 Serr Flange Locknut SS (Jar 100)

No. The flange does the washer's job: it measures 0.728 to 0.750 inch across the bearing face, and the serrations on its underside bite the work surface to resist loosening from vibration. That is why it is used on strut, enclosure and equipment mounting where you would otherwise stack a flat washer and a split lock washer under a plain hex nut. On soft or coated surfaces, remember the serrations will mar the finish.

It is a 3/8 inch nut with 16 threads per inch. Note that 16 TPI is not the UNC coarse pitch for 3/8 (that is 16 on some fastener lines but 3/8-16 is the pitch stated here), so match it to a 3/8 rod or bolt of the same 16 TPI thread. Mixing it onto a different pitch will cross-thread and strip the stainless.

These are 18-8 stainless steel, the standard austenitic grade used where plated carbon steel would rust out, so they suit damp interiors, exterior equipment mounts and washdown areas. 18-8 is not the choice for chloride-heavy coastal or pool chemical exposure, where 316 is the usual step up. Also keep in mind stainless on stainless threads can gall, so run them on without impact tools or use an anti-seize.

Metallics lists the JSFN3816SS as both Buy American compliant and ARRA compliant. Country of origin is China, so if your contract language requires domestic melt and manufacture rather than the compliance designation, confirm which standard the specification is written to before you submit.

It is built to ASME B18.16.4-2008, the dimensional standard for prevailing-torque and serrated flange lock nuts, so it interchanges with any other B18.16.4 3/8-16 serrated flange nut on the same thread. That matters on spec jobs where the submittal calls out a standard rather than a brand.

They ship in a jar of 100 count, and 100 count is the order minimum, so one jar is the smallest buy. A full jar weighs 1.91 lbs. Metallics does offer other sizes and quantities on request.

Yes, down to 0.04 inch panel thickness. The wide flange spreads the clamp load across 0.728 to 0.750 inch of bearing surface, which is what keeps the nut from dimpling or pulling through light-gauge sheet the way a plain hex nut will. On thinner material than 0.04 inch, back it with a larger load-spreading washer.

The locking action here is mechanical: serrations on the flange face dig into the joint surface, so the thread itself is clean and the nut spins off freely. That makes it faster to run down than a nylon insert nut, but the hold depends on the serrations having a solid surface to bite. Once they have flattened out, or if the mating surface is hardened, plated or already scored from a previous nut, replace rather than reuse.