PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

FF-B-561DScrew,lag

Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M · NSN 5305-00-407-6543 · FSC 5305 · No Item Name Available
Verified by PartsTable
NSN 5305-00-407-6543 — this item is cataloged by the U.S. Government under National Stock Number 5305-00-407-6543. Primary manufacturer part number: FF-B-561D.
Features
  • Screw,lag — FSC 5305
  • Nonmachine Thread Style: GIMLET POINT (TYPE A, AB OR BA)
  • Nonmachine Nominal Thread Diameter: 0.500 INCHES IN
  • Material Document and Classification: 66 FED STD ALL MATERIAL RESPONSES OVERALL
  • Width Between Flats: 0.750 INCHES NOMINAL IN
  • Head Height: 0.328 INCHES NOMINAL IN
  • Head Style: HEXAGON
  • Fastener Length: 4.500 INCHES NOMINAL IN
Applications
  • Structural fastening and assembly
  • Equipment mounting
  • Panel and housing attachment
  • Applications requiring Steel Comp 302 or Steel Comp 303 or Steel Comp 304 or Steel Comp 305 or Steel Comp 310 or Steel Comp 316 Overall construction
General Description

The Screw,lag, cataloged under National Stock Number 5305-00-407-6543, is classified within Federal Supply Class 5305 (No Item Name Available) of the Hardware and Abrasives group. The primary manufacturer of record is Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M. Government technical data includes 11 verified specifications, sourced from the Federal Logistics Information System (FLIS). This item has 3 commercial cross-references from 3 manufacturers, enabling identification through both NSN and commercial part number lookups. 11 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Active.

Technical Specifications
ParameterValue
NSN5305-00-407-6543
Primary Part NumberFF-B-561D
Item NameScrew,lag
FSC / FSG5305 / 53 — No Item Name Available
ManufacturerMilitary Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M
StatusACTIVE
Nonmachine Thread StyleGIMLET POINT (TYPE A, AB OR BA)
Nonmachine Nominal Thread Diameter0.500 INCHES IN
Material Document and Classification66 FED STD ALL MATERIAL RESPONSES OVERALL
Width Between Flats0.750 INCHES NOMINAL IN
Head Height0.328 INCHES NOMINAL IN
Head StyleHEXAGON
Fastener Length4.500 INCHES NOMINAL IN
Surface TreatmentPASSIVATE OVERALL
Nondefinitive Spec/std Data3 TYPE AND C GRADE
Test Data Document81348-STDNO151 DRAWING (THIS IS THE BASIC GOVERNING DRAWING, SUCH AS A CONTRACTOR DRAWING, ORIGINAL EQUIPMENT MANUFACTURER DRAWING, ETC.; EXCLUDES ANY SPECIFICATION, STANDARD OR OTHER DOCUMENT THAT MAY BE REFERENCED IN A BASIC GOVERNING DRAWING)
MaterialSTEEL COMP 302 OR STEEL COMP 303 OR STEEL COMP 304 OR STEEL COMP 305 OR STEEL COMP 310 OR STEEL COMP 316 OVERALL
Lifecycle & Compliance
Acquisition StatusACTIVE
HAZMATNo
Verified Substitutes 11
1650-00-130-93545371 INTERCHANGEABLE
Head,hydraulic Motor-Pump
Eaton Aerospace, Llc Dba Jackson South
5950-00-156-084610688212 INTERCHANGEABLE
Transformer,power
Us Army Aviation and Missile Command
5305-00-177-5624 INTERCHANGEABLE
Screw,lag
5330-00-251-32294001639-6 INTERCHANGEABLE
Gasket
Agco Corp Parts Opn
5305-00-406-5199 INTERCHANGEABLE
Screw,lag
5305-00-449-2240 INTERCHANGEABLE
Screw,lag
1280-00-595-36065371 INTERCHANGEABLE
Heat Plate,offset P
Cox & Company, Inc. Dba Cox & Co Inc
1630-01-240-4316537-1-1 INTERCHANGEABLE
Heat Stack Assembly
Goodrich Corporation Div Collins Aerospace, Landing Systems (wheels & Brakes)
5330-01-420-0704 INTERCHANGEABLE
Seal,nonmetallic Special Shaped
7045-01-515-537105745 INTERCHANGEABLE
Disk,nonflexible
Memorex Corp
Cross-Reference Index
Part NumberManufacturer
FF-B-561D Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M
FFB561TYPEVGRADEC Federal Specifications Promulgated by General Services Administration Washington DC (USA)
5371 Utilities Service Co Sub of Lehigh Structural Steel Co (USA)
Related Parts
1650-00-130-9354INTERCHANGEABLE
HEAD,HYDRAULIC MOTOR-PUMP
5371
5950-00-156-0846INTERCHANGEABLE
TRANSFORMER,POWER
10688212
5305-00-177-5624INTERCHANGEABLE
SCREW,LAG
5330-00-251-3229INTERCHANGEABLE
GASKET
4001639-6
5305-00-406-5199INTERCHANGEABLE
SCREW,LAG
5305-00-449-2240INTERCHANGEABLE
SCREW,LAG
1280-00-595-3606INTERCHANGEABLE
HEAT PLATE,OFFSET P
5371
1630-01-240-4316INTERCHANGEABLE
HEAT STACK ASSEMBLY
537-1-1
5330-01-420-0704INTERCHANGEABLE
SEAL,NONMETALLIC SPECIAL SHAPED
7045-01-515-5371INTERCHANGEABLE
DISK,NONFLEXIBLE
05745
6515-01-559-3980INTERCHANGEABLE
FORCEPS,HEMOSTATIC
VM25-2509

Frequently Asked Questions

What is NSN 5305-00-407-6543?

NSN 5305-00-407-6543 is a Screw,lag, manufactured by Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M, classified under FSC 5305 (No Item Name Available). Status: active.

What are the part numbers for NSN 5305-00-407-6543?

NSN 5305-00-407-6543 has 3 cross-referenced part numbers: FF-B-561D (Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M), FFB561TYPEVGRADEC (Federal Specifications Promulgated by General Services Administration Washington DC), 5371 (Utilities Service Co Sub of Lehigh Structural Steel Co).

What NSN replaces 5305-00-407-6543?

There are 11 known substitutes for 5305-00-407-6543: 1650-00-130-9354, 5950-00-156-0846, 5305-00-177-5624 and 8 more. Verify interchangeability with system specifications before substitution.

What are the specifications of FF-B-561D?

Key specifications for FF-B-561D: Nonmachine Thread Style: GIMLET POINT (TYPE A, AB OR BA); Nonmachine Nominal Thread Diameter: 0.500 INCHES IN; Material Document and Classification: 66 FED STD ALL MATERIAL RESPONSES OVERALL; Width Between Flats: 0.750 INCHES NOMINAL IN. 11 total characteristics are documented in the Federal Logistics Information System.

Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
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