The Washer,recessed, cataloged under National Stock Number 5310-01-076-9428, is classified within Federal Supply Class 5310 (Nuts and Washers) of the Hardware and Abrasives group. The manufacturer of record is Northrop Grumman Systems Corporation. Government technical data includes 12 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through both NSN and commercial part number lookups. 2 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5310-01-076-9428 |
| Primary Part Number | A51B21644-21 |
| Item Name | Washer,recessed |
| FSC / FSG | 5310 / 53 — Nuts and Washers |
| Manufacturer | Northrop Grumman Systems Corporation |
| Status | ACTIVE |
| Surface Finish | 125.0 MICROINCHES ALL SURFACES |
| Surface Treatment Document and Classification | MIL-C-8837,TYPE 2,CLASS 1 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL |
| Hardness Rating | 46.0 ROCKWELL C MINIMUM AND 49.0 ROCKWELL C MAXIMUM |
| Style Designator | RECESSED |
| Material Document and Classification | G-1013,COMP D6AC MFR REF SINGLE MATERIAL RESPONSE OVERALL |
| Outside Diameter | 1.550 INCHES NOMINAL IN |
| Material Thickness | 0.270 INCHES NOMINAL IN |
| Recess Diameter | 1.014 INCHES NOMINAL IN |
| Surface Treatment | CADMIUM OVERALL |
| Material | STEEL OVERALL |
| Hole Diameter | 0.514 INCHES MINIMUM AND 0.523 INCHES MAXIMUM IN |
| Recess Angle | 100.0 DEGREES NOMINAL |
| 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 |
|---|---|
| A51B21644-21 PRIMARY | Northrop Grumman Systems Corporation (USA) |
| Reference | Meaning |
|---|---|
| A51B21644-21 | 3/9 Design control — primary reference Northrop Grumman Systems Corporation Dba Northrop Grumman Systems Corp Div Northrop Grumman Aeronautics Systems |
| A51B21644-21 | 5/9 Secondary reference Northrop Grumman Systems Corporation |
NSN 5310-01-076-9428 is a Washer,recessed, manufactured by Northrop Grumman Systems Corporation, classified under FSC 5310, Nuts and Washers. Status: active.
NSN 5310-01-076-9428 has 1 manufacturer part number on file: A51B21644-21 (Northrop Grumman Systems Corporation).
Key specifications for A51B21644-21: Surface Finish: 125.0 MICROINCHES ALL SURFACES; Surface Treatment Document and Classification: MIL-C-8837,TYPE 2,CLASS 1 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL; Hardness Rating: 46.0 ROCKWELL C MINIMUM AND 49.0 ROCKWELL C MAXIMUM; Style Designator: RECESSED. 12 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.