The Screw,close Tolerance, cataloged under National Stock Number 5305-01-016-9638, is classified within Federal Supply Class 5305 (Screws) of the Hardware and Abrasives group. The manufacturer of record is Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company. Government technical data includes 19 specifications, cited from the U.S. Government catalog. The record lists 6 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through both NSN and commercial part number lookups. 4 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog.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 | 5305-01-016-9638 |
| Primary Part Number | 51B581-4-1 |
| Item Name | Screw,close Tolerance |
| FSC / FSG | 5305 / 53 — Screws |
| Manufacturer | Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company |
| Status | ACTIVE |
| Surface Finish | 32.0 MICROINCHES GRIP |
| Fastener Length | 0.362 INCHES MINIMUM AND 0.409 INCHES MAXIMUM IN |
| Surface Treatment Document and Classification | QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL |
| Thread Length | 0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN |
| Hardness Rating | 39.0 ROCKWELL C MINIMUM AND 43.0 ROCKWELL C MAXIMUM OVERALL |
| Nominal Thread Diameter | 0.250 INCHES IN |
| Head Style | FLAT COUNTERSUNK |
| Thread Direction | RIGHT-HAND |
| Grip Length | 0.052 INCHES MINIMUM AND 0.072 INCHES MAXIMUM IN |
| Grip Diameter | 0.2485 INCHES MINIMUM AND 0.2495 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) |
| Countersink Angle | 100.0 DEGREES NOMINAL |
| Thread Class | 3A A |
| Thread Quantity Per Inch | 28 |
| Material | STEEL COMP 4340 OR STEEL COMP 4140 OR STEEL COMP 8740 OVERALL |
| Thread Series Designator | UNIFIED NATIONAL JOINT FINE (UNJF) |
| Head Diameter | 0.389 INCHES MINIMUM AND 0.394 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 |
|---|---|
| 51B581-4-1 | Northrop Grumman Corp Electronic Systems Defensive System Div (USA) |
| 51B581-4-1 PRIMARY | Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company (USA) |
| 51B581-4-1 | Lisi Aerospace Canada Corp Div Hi Shear Holdings Inc (CAN) |
| 51B581-4-1 | Sps Technologies Llc Dba PB Fasteners Div PB Fasteners (USA) |
| 51B581-4-1 | Hi-Shear Corporation (USA) |
| 51B581-4-1 | Howmet Global Fastening Systems Inc (USA) |
| Reference | Meaning |
|---|---|
| 51B581-4-1 | 5/9 Secondary reference Deutsch Fastener Corp |
| 51B581-4-1 | 7/9 Vendor item drawing reference Northrop Grumman Systems Corporation Dba Northrop Grumman Is Div Northrop Grumman Aeronautics Systems |
| 51B581-4-1 | 5/2 Secondary reference U.S. Government activity |
| 51B581-4-1 | C/1 Advisory reference — outside the item-of-supply concept Northrop Grumman Technical Services, Inc. Dba Defense Systems Sector |
NSN 5305-01-016-9638 is a Screw,close Tolerance, manufactured by Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company, classified under FSC 5305, Screws. Status: active.
NSN 5305-01-016-9638 has 6 manufacturer part numbers on file: 51B581-4-1 (Northrop Grumman Corp Electronic Systems Defensive System Div), 51B581-4-1 (Sps Technologies, Llc Dba Air Industries Company Div Air Industries Company), 51B581-4-1 (Lisi Aerospace Canada Corp Div Hi Shear Holdings Inc), 51B581-4-1 (Sps Technologies Llc Dba PB Fasteners Div PB Fasteners), 51B581-4-1 (Hi-Shear Corporation) and 1 more.
Key specifications for 51B581-4-1: Surface Finish: 32.0 MICROINCHES GRIP; Fastener Length: 0.362 INCHES MINIMUM AND 0.409 INCHES MAXIMUM IN; Surface Treatment Document and Classification: QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL; Thread Length: 0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN. 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.