Metallics NYN163B Nuts 1/4-20 Hx Ny-Ins Locknut St-zn (Box 3500)

It's a 1/4-20 nut, 20 threads per inch on a 1/4 inch diameter, cut to the ANSI/ASME B1.1 unified thread standard. Any standard 1/4-20 UNC bolt, screw, or threaded rod will take it.

They ship as a box of 3,500 pieces, and 3,500 is also the order minimum, so it's a full-box buy rather than a loose count. The box weighs 29.4 lbs.

Metallics lists the NYN163B as both Buy American compliant and ARRA compliant, which is what a public-agency or federally funded spec usually asks for. Country of origin is listed as multiple, so if your contract requires a single named origin, that needs confirming on the specific shipment.

The nut is steel with a zinc finish, which gives moderate corrosion resistance for dry interior and protected exterior work. For continuous wet, coastal, or chemically aggressive locations, zinc-plated steel is not the right call; specify a stainless or hot-dip galvanized nylon insert locknut instead.

A nylon insert nut resists loosening from vibration by deforming the nylon collar around the bolt threads, so it needs no separate washer and seats flush. Two limits worth knowing: the nylon loses its grip after repeated reuse, and heat degrades it, so for high-temperature assemblies or joints you expect to break and remake many times, an all-metal prevailing torque nut or a plain hex nut with a lock washer is the better pick.

Dimensions follow ASME B18.16.6, the standard for prevailing torque nuts, so the hex, height, and bearing face match any other B18.16.6 1/4-20 nylon insert nut already on your assemblies. That is what lets you mix boxes from different lots without a wrench change.

Nylon end last. The nylon collar sits at one end of the nut, so run the plain steel threaded end onto the bolt first and let the bolt drive through the nylon as it tightens. The bolt should emerge fully through the collar for the lock to work.