The Screw,close Tolerance, cataloged under National Stock Number 5305-00-802-0571, is classified within Federal Supply Class 5305 (Screws) of the Hardware and Abrasives group. The manufacturer of record is Hi-Shear Corporation. Government technical data includes 19 specifications, cited from the U.S. Government catalog. The record lists 5 manufacturer part numbers for this item, enabling identification through both NSN and commercial part number lookups. 4 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5305-00-802-0571 |
| Primary Part Number | 51B221-5 |
| Item Name | Screw,close Tolerance |
| FSC / FSG | 5305 / 53 — Screws |
| Manufacturer | Hi-Shear Corporation |
| Status | ACTIVE |
| Surface Finish | 32.0 MICROINCHES GRIP |
| Head Height | 0.103 INCHES MINIMUM AND 0.118 INCHES MAXIMUM IN |
| Fastener Length | 0.573 INCHES MINIMUM AND 0.620 INCHES MAXIMUM IN |
| Surface Treatment Document and Classification | QQ-P-416,TYPE 2,CLASS 3 FED SPEC SINGLE TREATMENT RESPONSE OVERALL |
| Thread Length | 0.276 INCHES MINIMUM IN |
| Material Document and Classification | MIL-S-5626 MIL SPEC 1ST MATERIAL RESPONSE OR MIL-S-5000 MIL SPEC 2ND MATERIAL RESPONSE OR MIL-S-8503 MIL SPEC 3RD MATERIAL RESPONSE OR MIL-S-6098 MIL SPEC 4TH MATERIAL RESPONSE OR MIL-S-6049 MIL SPEC 5TH MATERIAL RESPONSE OVERALL |
| Nominal Thread Diameter | 0.190 INCHES IN |
| Head Style | MODIFIED PAN |
| Thread Direction | RIGHT-HAND |
| Grip Length | 0.297 INCHES MINIMUM AND 0.327 INCHES MAXIMUM IN |
| Grip Diameter | 0.1885 INCHES MINIMUM AND 0.1895 INCHES MAXIMUM IN |
| Surface Treatment | CADMIUM AND CHROMATE OVERALL |
| Minimum Tensile Strength | 180000 POUNDS PER SQUARE INCH LBS |
| Internal Drive Style | OFFSET CRUCIFORM (TORQUE SET) |
| Thread Class | 3A A |
| Thread Quantity Per Inch | 32 |
| Material | STEEL COMP 4140 OR STEEL COMP E4340 OR STEEL COMP 6150 OR STEEL COMP 8735 OR STEEL COMP 8740 OVERALL |
| Thread Series Designator | UNF |
| Head Diameter | 0.361 INCHES MINIMUM AND 0.381 INCHES MAXIMUM IN |
| 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 |
|---|---|
| 51B221-5 | Hi-Shear Corporation (USA) |
| 51B221-5 | Howmet Global Fastening Systems Inc (USA) |
| 51B221-5 | Lisi Aerospace Canada Corp Div Hi Shear Holdings Inc (CAN) |
| 51B221-5 | Sps Technologies Llc Dba PB Fasteners Div PB Fasteners (USA) |
| 51B221-5 | Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company (USA) |
| Reference | Meaning |
|---|---|
| 51B221-5 | 3/9 Design control — primary reference Northrop Grumman Systems Corporation Dba Northrop Grumman Is Div Northrop Grumman Aeronautics Systems |
| 51B221-5 | C/1 Advisory reference — outside the item-of-supply concept Northrop Grumman Technical Services, Inc. Dba Defense Systems Sector |
| 51B221-5 | 5/2 Secondary reference U.S. Government activity |
| 51B221-5 | 5/2 Secondary reference U.S. Government activity |
NSN 5305-00-802-0571 is a Screw,close Tolerance, manufactured by Hi-Shear Corporation, classified under FSC 5305, Screws. Status: active.
NSN 5305-00-802-0571 has 5 manufacturer part numbers on file: 51B221-5 (Hi-Shear Corporation), 51B221-5 (Howmet Global Fastening Systems Inc), 51B221-5 (Lisi Aerospace Canada Corp Div Hi Shear Holdings Inc), 51B221-5 (Sps Technologies Llc Dba PB Fasteners Div PB Fasteners), 51B221-5 (Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company).
Key specifications for 51B221-5: Surface Finish: 32.0 MICROINCHES GRIP; Head Height: 0.103 INCHES MINIMUM AND 0.118 INCHES MAXIMUM IN; Fastener Length: 0.573 INCHES MINIMUM AND 0.620 INCHES MAXIMUM IN; Surface Treatment Document and Classification: QQ-P-416,TYPE 2,CLASS 3 FED SPEC SINGLE TREATMENT RESPONSE OVERALL. 19 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.