Metallics SFN1420B Nuts 1/4-20 Serr Flange Locknut St-zn (Box 5000)

Yes. The SFN1420B is a 1/4 inch serrated flange lock nut cut at 20 threads per inch, which is the standard 1/4-20 UNC coarse thread. It mates with any 1/4-20 bolt, screw or threaded rod. It will not fit 1/4-28 fine thread.

No separate washer is needed. The flange on this Metallics nut spreads the load itself, with a bearing diameter of 0.574 to 0.594 inch, and the serrations on the underside bite the mating surface as you torque it down. A flat washer under a serrated flange actually defeats the locking action, since the teeth need to dig into the workpiece.

The hex across the flats measures 0.428 to 0.438 inch, so a 7/16 inch socket or wrench is the fit. Overall across the flange it runs 0.488 to 0.505 inch, which matters when you are working in a tight pocket, and the nut stands 0.222 to 0.236 inch tall.

It is built to ASME B18.16.4-2008, the dimensional standard for prevailing-torque and free-spinning flange lock nuts, so hex size, flange diameter and height match any other nut made to that same standard. That makes it a drop-in for existing 1/4-20 flange nut assemblies.

It is low carbon steel with a zinc plating, which handles indoor, dry and normally damp interior work and light exterior exposure. For wet, coastal or chemically aggressive locations, step up to 18-8 stainless rather than zinc-plated steel.

The serrated flange works mechanically on the joint face: the teeth bite the mating surface and it takes more torque to back the nut off than it did to run it on. That means no plastic element to degrade, so it tolerates heat and can be run with a gun. A nylon insert locks on the bolt threads instead and is the better choice when you cannot mar the mating surface or need to reuse the nut repeatedly. One more thing this design gives you: the flange will span an oversized or poorly aligned hole, and it does not gall the screw threads.

The SFN1420B ships as a box of 5,000 pieces, which is also the order minimum, and the box weighs 44.3 lbs. Metallics notes other sizes and quantities are available by request, so if you need a smaller count or a different thread size, ask.

Metallics lists the SFN1420B as both Buy American compliant and ARRA compliant, which is what a government or institutional spec usually asks for on the submittal. Country of origin is listed as multiple.

Surface hardness is Rockwell HR15N 78 to 90, the range specified for low carbon steel flange lock nuts of this class. Pair them with commercial grade 1/4-20 bolts. On a high strength hardened bolt being torqued to its full rating, the nut is the weaker element, so specify a matching higher grade nut instead.