Fasteners & Fastening Hardware

Fasteners and fastening hardware — screws, nuts, washers, pins, and threaded inserts — are among the most tightly specified items in the federal supply system. Each is built to a published Military Standard or federal specification that fixes its dimensions, thread form, material, and finish, so a single MS number identifies exactly one part regardless of who manufactures it. That precision is the point: a fastener called out on a drawing or a bill of materials has to interchange with every other part built to the same spec, from any qualified source.

Ordering starts from whichever identifier is in hand. An MS or federal spec number resolves to a National Stock Number (NSN), and the NSN carries the part’s full federal record — technical characteristics, manufacturer cross-references, and, where applicable, supersession history back to earlier or cancelled part numbers. A buyer working from an old drawing, a torn label, or a cross-reference sheet can arrive at the same part through any of those paths.

This class covers the hardware that shows up on nearly every airframe, ground-support rig, and mechanical assembly: self-locking and plain nuts, lock and key washers, machine screws, cotter pins, and the fastening devices — inserts, retainers — that go with them. Atlas Air Supply stocks and quotes this hardware against its governing specification under CAGE 224F0; every item’s full federal record is available before a quote is requested.

What’s the difference between a self-locking nut and a plain nut?

A self-locking nut has a built-in feature — a nylon insert or a deformed section of thread — that grips the bolt and resists loosening under vibration without any separate lock washer. A plain nut has no such feature; it relies on thread friction alone, or on a separate locking element (a lock washer, a cotter pin through a castellated nut) specified alongside it. Which one a drawing calls for is fixed by the part’s MS number, not by the shape of the nut alone.

How do I identify a screw thread size from a part number?

The MS or federal spec number ties to a published drawing that fixes thread size, pitch, material, and finish — that information isn’t encoded readable-at-a-glance in the digits of the part number itself. Cross-referencing the number (or the NSN it resolves to) against its federal record confirms the exact thread specification, rather than inferring it from the part number’s format.