The Nut,self-Locking,extended Washer, cataloged under National Stock Number 5310-01-223-6531, is classified within Federal Supply Class 5310 (Nuts and Washers) of the Hardware and Abrasives group. The manufacturer of record is Huck International, Inc. Government technical data includes 17 specifications, cited from the U.S. Government catalog. The record lists 3 manufacturer part numbers for this item, enabling identification through both NSN and commercial part number lookups. 3 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5310-01-223-6531 |
| Primary Part Number | KFN556-3 |
| Item Name | Nut,self-Locking,extended Washer |
| FSC / FSG | 5310 / 53 — Nuts and Washers |
| Manufacturer | Huck International, Inc |
| Status | ACTIVE |
| Washer Outside Diameter | 0.348 INCHES MAXIMUM IN |
| Width Across Flats | 0.243 INCHES MINIMUM AND 0.251 INCHES MAXIMUM IN |
| Surface Treatment Document and Classification | QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE NUT |
| Thread Series | UNIFIED NATIONAL JOINT FINE (UNJF) |
| Hardness Rating | 39.0 ROCKWELL C MINIMUM AND 43.0 ROCKWELL C MAXIMUM |
| Washer Thickness | 0.088 INCHES MINIMUM AND 0.092 INCHES MAXIMUM IN |
| Material Document and Classification | MIL-P-19468 MIL SPEC SINGLE MATERIAL RESPONSE WASHER |
| Material Document and Classification | MIL-S-6049 MIL SPEC 1ST MATERIAL RESPONSE OR MIL-S-5000 MIL SPEC 2ND MATERIAL RESPONSE NUT |
| Thread Direction | RIGHT-HAND |
| Nominal Thread Size | 0.190 INCHES IN |
| Locking Feature | PREVAILING TORQUE ALL METAL DESIGN |
| Surface Treatment | CADMIUM AND CHROMATE NUT |
| Nut Style | HEXAGON |
| Thread Class | 3B |
| Thread Quantity Per Inch | 32 |
| Material | PLASTIC POLYTETRAFLUOROETHYLENE WASHER |
| Material | STEEL COMP 8740 OR STEEL COMP E4340 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 |
|---|---|
| KFN556-3 | Bristol Industries, Llc (USA) |
| KFN556-3 | Howmet Global Fastening Systems Inc (USA) |
| KFN556-3 PRIMARY | Huck International, Inc (USA) |
| Reference | Meaning |
|---|---|
| BH00529-3 | 5/9 Secondary reference Bristol Industries, Llc |
| KFN556-3 | 5/9 Secondary reference Vsi Corp Sub of Fairchild Industries Inc |
| KFN556-3 | 3/2 Design control — primary reference U.S. Government activity |
NSN 5310-01-223-6531 is a Nut,self-Locking,extended Washer, manufactured by Huck International, Inc, classified under FSC 5310, Nuts and Washers. Status: active.
NSN 5310-01-223-6531 has 3 manufacturer part numbers on file: KFN556-3 (Bristol Industries, Llc), KFN556-3 (Howmet Global Fastening Systems Inc), KFN556-3 (Huck International, Inc).
Key specifications for KFN556-3: Overall Height: 0.301 INCHES MAXIMUM IN; Washer Outside Diameter: 0.348 INCHES MAXIMUM IN; Width Across Flats: 0.243 INCHES MINIMUM AND 0.251 INCHES MAXIMUM IN; Surface Treatment Document and Classification: QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE NUT. 17 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.