The Nut,self-Locking,assembled Washe, cataloged under National Stock Number 5310-01-221-7020, is classified within Federal Supply Class 5310 (Nuts and Washers) of the Hardware and Abrasives group. The manufacturer of record is Howmet Global Fastening Systems Inc. Government technical data includes 18 specifications, cited from the U.S. Government catalog. The record lists 1 manufacturer part number for this item, enabling identification through both NSN and commercial part number lookups. 1 additional reference document (drawings, advisory and superseded references) is recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5310-01-221-7020 |
| Primary Part Number | KFN542-4S |
| Item Name | Nut,self-Locking,assembled Washe |
| FSC / FSG | 5310 / 53 — Nuts and Washers |
| Manufacturer | Howmet Global Fastening Systems Inc |
| Status | ACTIVE |
| Washer Outside Diameter | 0.460 INCHES MAXIMUM IN |
| Width Across Flats | 0.306 INCHES MINIMUM AND 0.313 INCHES MAXIMUM IN |
| Surface Treatment Document and Classification | QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL |
| Thread Series | UNIFIED NATIONAL JOINT FINE (UNJF) |
| Temp Rating | 450.0 FAHRENHEIT MAXIMUM DEGF |
| Hardness Rating | 39.0 ROCKWELL C MINIMUM AND 43.0 ROCKWELL C MAXIMUM |
| Material Document and Classification | MIL-S-5000 MIL SPEC 1ST MATERIAL RESPONSE OR MIL-S-5626 MIL SPEC 2ND MATERIAL RESPONSE OR MIL-S-6049 MIL SPEC 3RD MATERIAL RESPONSE NUT |
| Nut Counterbore Depth | 0.087 INCHES MINIMUM AND 0.097 INCHES MAXIMUM NUT IN |
| Thread Direction | RIGHT-HAND |
| Nominal Thread Size | 0.250 INCHES IN |
| Counterbore Diameter | 0.283 INCHES MINIMUM AND 0.288 INCHES MAXIMUM NUT IN |
| Locking Feature | FREE-RUNNING ALL METAL DESIGN |
| Surface Treatment | CADMIUM AND CHROMATE OVERALL |
| Nut Style | FLAT WITH TURNED UP EDGE |
| Thread Class | 3B |
| Thread Quantity Per Inch | 28 |
| Material | STEEL WASHER |
| Material | STEEL COMP E4340 OR STEEL COMP 4140 OR STEEL COMP 8740 NUT |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL A — No Demilitarization Required |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| KFN542-4S PRIMARY | Howmet Global Fastening Systems Inc (USA) |
| Reference | Meaning |
|---|---|
| KFN542-4S | 5/9 Secondary reference Howmet Global Fastening Systems Inc. Div Microdot Products |
NSN 5310-01-221-7020 is a Nut,self-Locking,assembled Washe, manufactured by Howmet Global Fastening Systems Inc, classified under FSC 5310, Nuts and Washers. Status: active.
NSN 5310-01-221-7020 has 1 manufacturer part number on file: KFN542-4S (Howmet Global Fastening Systems Inc).
Key specifications for KFN542-4S: Overall Height: 0.280 INCHES NOMINAL IN; Washer Outside Diameter: 0.460 INCHES MAXIMUM IN; Width Across Flats: 0.306 INCHES MINIMUM AND 0.313 INCHES MAXIMUM IN; Surface Treatment Document and Classification: QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL. 18 specifications are documented in the U.S. Government catalog.
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.