Part Number
Socket Head Cap Screw · NAS (National Aerospace Standard) · NSN 5305-01-210-9429
| Part number | NAS1351-4-21 |
|---|---|
| Specification family | NAS (National Aerospace Standard) |
| Item name | Socket Head Cap Screw |
| Alternate references | NAS1351-21; 0645-0428-21UDK |
| Unit of issue | EA |
| Cross-referenced NSN | 5305-01-210-9429 |
| Federal Supply Class (FSC) | 5305 — Screws |
| Unit price (USD) | $2.62 |
| 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 socket head cap screw. Confirm controlling dimensions against your drawing or standard sheet before ordering.
| Fastener Length | 1.296 Inches Minimum And 1.343 Inches Maximum |
|---|---|
| Hardness Rating | 36.0 Rockwell C Minimum And 43.0 Rockwell C Maximum Overall |
| Head Style | Flat Chamfer |
| Material | Steel Overall |
| Nominal Thread Diameter | 0.250 Inches |
| Surface Treatment | Oxide Overall |
| Thread Class | 3A |
| Thread Series Designator | Unf |
Externally threaded fasteners designed to be turned to assemble or adjust parts, including machine screws, cap screws, socket-head cap screws, set screws, self-tapping and thread-forming screws. This is the largest single class in the U.S. supply system and covers a vast range of thread sizes, drive types, head styles, and materials.
Reading the part number. NAS1351-4-21 breaks down as NAS1351 — the National Aerospace Standard that fixes the part's design — plus the dash/suffix code 4-21, which selects the exact size, material, or finish variant from the tables on that standard. Two parts sharing the NAS1351 base are the same design in different variants.
Price in context. Across the 2,357 items we currently stock in FSC 5305 (Screws), published unit prices run from $0.03 to $14,752.17. At $2.62, this item sits well below the class median of $10.52 — commodity hardware usually bought in volume.
Who orders NAS1351-4-21. Aircraft owners and MRO shops replacing standard hardware, machine shops and OEMs filling a bill of materials, and government contractors sourcing against NSN 5305-01-210-9429. 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 B18.3 / B18.6.3, MIL-DTL / NASM / MS and AN series, ISO metric threads; common materials include carbon and alloy steel, 300/400-series stainless, and A2/A4 stainless per ISO 3506.
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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