Part Number
Plate Self-Locking Nut · MS (Military Standard) · NSN 5310-00-777-5771
| Part number | MS21059-4K |
|---|---|
| Specification family | MS (Military Standard) |
| Item name | Plate Self-Locking Nut |
| Alternate references | MS21059-4K-RF200X4K-RF20X4K-T65S428SBCPC; 13650NM-048BC; F52LHTA521-048BC; RF200X4K; RF20X4K; T65S428SBCPC |
| Unit of issue | EA |
| Cross-referenced NSN | 5310-00-777-5771 |
| Federal Supply Class (FSC) | 5310 — Nuts and Washers |
| Unit price (USD) | $1.75 |
| Country of origin | Türkiye (Turkey) |
| Lead time | Within 90 days of order |
| Minimum order | May apply — confirm on quote |
| Documentation | Source documentation provided on all orders |
Characteristics decoded from the federal cataloging record for this plate self-locking nut. Confirm controlling dimensions against your drawing or standard sheet before ordering.
| Hardness Rating | 49.0 Rockwell C Maximum |
|---|---|
| Material | Steel Overall |
| Surface Treatment | Cadmium Overall |
| Thread Class | 3B |
| Thread Quantity Per Inch | 28 |
Internally threaded fasteners (hex nuts, lock nuts, castle nuts, wing nuts, self-locking nuts) and washers (flat, lock, spring, and special washers) used to distribute load and secure threaded assemblies.
Reading the part number. MS21059-4K breaks down as MS21059 — the Military Standard sheet that fixes the part's design — plus the dash/suffix code 4K, which selects the exact size, material, or finish variant from the tables on that standard. Two parts sharing the MS21059 base are the same design in different variants.
Price in context. Across the 1,144 items we currently stock in FSC 5310 (Nuts and Washers), published unit prices run from $0.12 to $68,673.00. At $1.75, this item sits well below the class median of $8.76 — commodity hardware usually bought in volume.
Who orders MS21059-4K. Aircraft owners and MRO shops replacing standard hardware, machine shops and OEMs filling a bill of materials, and government contractors sourcing against NSN 5310-00-777-5771. You can order by part number or by stock number — it is the same item, the same published price, and the same quote form.
Applicable standards. ASME B18.2.2 / B18.16, B18.21 / B18.22, NASM/MS series; steel, stainless, and self-locking (nylon-insert and all-metal) designs.
Need this part modified, or a similar part made to your print? See our U.S.-based CNC machining services and aerospace machining capability.
Country of origin: Türkiye (Turkey). Turkey is a NATO ally and a normal-trade-relations partner of the United States, and Turkish-origin end items are eligible for a wide range of U.S. federal and DLA procurements.
TAA note: Turkey is not a Trade Agreements Act (TAA) designated country, so these items are generally not eligible for TAA-covered solicitations. They are offerable under the Buy American Act and many non-TAA DLA buys. Buyers are responsible for confirming the origin requirements of their specific solicitation.
Full country-of-origin and source documentation is provided with every order. Fulfillment within 90 days of order. Minimum order may apply.
Items are supplied as stock mil-spec / commercial hardware with source documentation and country-of-origin paperwork on every order. Parts are not supplied with an FAA Form 8130-3 airworthiness tag unless expressly stated on the quote. Buyers installing hardware on certificated aircraft are responsible for acceptance under their own maintenance program, repair station procedures, or owner/operator authority.
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