The Bolt,machine, cataloged under National Stock Number 5306-00-121-2671, is classified within Federal Supply Class 5306 (Bolts) of the Hardware and Abrasives group. The manufacturer of record is Leonardo Spa Helicopters Division - Production Site. Government technical data includes 22 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through both NSN and commercial part number lookups. 1 additional reference document (drawings, advisory and superseded references) is recorded in the U.S. Government catalog. 1 item shares a part number with this NSN in the catalog (possible match — not a government interchangeability claim). Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5306-00-121-2671 |
| Primary Part Number | MS9557-06 |
| Item Name | Bolt,machine |
| FSC / FSG | 5306 / 53 — Bolts |
| Manufacturer | Leonardo Spa Helicopters Division - Production Site |
| Status | ACTIVE |
| Surface Finish | 32.0 MICROINCHES THREADS |
| Surface Finish | 32.0 MICROINCHES GRIP |
| Surface Finish | 32.0 MICROINCHES BEARING SURFACE OF HEAD |
| Extended Washer Thickness | 0.060 INCHES MINIMUM AND 0.070 INCHES MAXIMUM IN |
| Head Height | 0.300 INCHES NOMINAL IN |
| Fastener Length | 0.500 INCHES NOMINAL IN |
| Extended Washer Diameter | 0.438 INCHES NOMINAL IN |
| Thread Length | 0.401 INCHES MINIMUM AND 0.421 INCHES MAXIMUM IN |
| Hardness Rating | 248.0 BRINELL STANDARD MINIMUM AND 341.0 BRINELL STANDARD MAXIMUM OVERALL |
| Material Document and Classification | AMS 5731 ASSN STD SINGLE MATERIAL RESPONSE OVERALL |
| Nominal Thread Diameter | 0.250 INCHES IN |
| Features Provided | FINISHED HEAD |
| Head Style | DOUBLE HEXAGON W/HOLE |
| Thread Direction | RIGHT-HAND |
| Grip Length | 0.079 INCHES MINIMUM AND 0.099 INCHES MAXIMUM IN |
| Width Between Flats | 0.305 INCHES MINIMUM AND 0.313 INCHES MAXIMUM IN |
| Minimum Tensile Strength | 130000 POUNDS PER SQUARE INCH LBS |
| Minimum Yield Strength | 85000 POUNDS PER SQUARE INCH LBS |
| Thread Class | 3A A |
| Thread Quantity Per Inch | 28 |
| Material | IRON ALLOY 660 OVERALL |
| Thread Series Designator | UNIFIED NATIONAL JOINT FINE (UNJF) |
| 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 |
|---|---|
| MS9557-06 | Leonardo Spa Helicopters Division - Production Site (ITA) |
| Reference | Meaning |
|---|---|
| MS9557-06 | 2/2 Government specification standardization U.S. Government activity |
NSN 5306-00-121-2671 is a Bolt,machine, manufactured by Leonardo Spa Helicopters Division - Production Site, classified under FSC 5306, Bolts. Status: active.
NSN 5306-00-121-2671 has 1 manufacturer part number on file: MS9557-06 (Leonardo Spa Helicopters Division - Production Site).
1 possible match (shared part number, not a government interchangeability claim): 5306-01-497-4206. Verify interchangeability with system specifications before substitution.
Key specifications for MS9557-06: Surface Finish: 32.0 MICROINCHES THREADS; Surface Finish: 32.0 MICROINCHES GRIP; Surface Finish: 32.0 MICROINCHES BEARING SURFACE OF HEAD; Extended Washer Thickness: 0.060 INCHES MINIMUM AND 0.070 INCHES MAXIMUM IN. 22 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.