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PartsTable / COMPONENT / FF-B-561
FF-B-561 ✓ Verified by PartsTable
— · BOLT SCREW
WHAT YOU NEED TO KNOW
Grade/class stamped on head determines strength Metric and imperial threads look similar — measure pitch
Verify thread pitch — metric != imperial
PRODUCT OVERVIEW

The SCREW,LAG is a the manufacturer industrial component. Key specifications include material: STEEL OVERALL, head_style: HEXAGON, head_height: 0.226 INCHES MINIMUM AND 0.268 INCHES MAXIMUM IN, shoulder_shape: ROUND FIRST SHOULDER, fastener_length: 1.750 INCHES NOMINAL IN, hardness_rating: 60.0 ROCKWELL B MINIMUM OVERALL. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5305-00-009-1797, indicating validated use in U.S. government and defense logistics supply chains. Available through authorized enterprise resellers and TPM (Third Party Maintenance) channels.

Verify compatibility with your specific system configuration before ordering.

WHERE IT FITS
FF-B-561
NSN: 5305-00-009-1797
FSC: 5305
CAGE: 81348 — FEDERAL SPECIFICATIONS PROMULGATED BY GENERAL SERVICES ADMINISTRATION WASHINGTON DC (USA)
SPECIFICATIONS
materialSTEEL OVERALL
head_styleHEXAGON
head_height0.226 INCHES MINIMUM AND 0.268 INCHES MAXIMUM IN
shoulder_shapeROUND FIRST SHOULDER
fastener_length1.750 INCHES NOMINAL IN
hardness_rating60.0 ROCKWELL B MINIMUM OVERALL
shoulder_length0.125 INCHES MINIMUM FIRST SHOULDER IN
special_featuresTHREADS: 9 THREADS PER INCH
shoulder_diameter0.360 INCHES MINIMUM AND 0.388 INCHES MAXIMUM FIRST SHOULDER IN
surface_treatmentZINC OVERALL
width_between_flats0.544 INCHES MINIMUM AND 0.562 INCHES MAXIMUM IN
nonmachine_thread_styleGIMLET POINT (TYPE A, AB OR BA)
NSN5305-00-009-1797
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: FF-B-561 · OEM ⚠ VERIFY BEFORE ORDERING Verify thread pitch before ordering — metric (M8×1.25) ≠ imperial (5/16-18). Wrong thread = wrong part. Grade/class stamped on bolt head determines tensile strength ✓ BROKER TIP Grade/class stamped on head determines tensile strength. Grade 8 > Grade 5 > Grade 2. Always confirm head marking matches specification requirement PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
MATERIAL DOCUMENT AND CLASSIFICATION: FF-B-561,GRADE B FED SPEC SINGLE MATERIAL RESPONSE OVERALL
•
MINIMUM TENSILE STRENGTH: 55000 POUNDS PER SQUARE INCH LBS
•
NONDEFINITIVE SPEC/STD DATA: 1 TYPE AND 1 STYLE AND B GRADE
•
SHOULDER DIAMETER: 0.237 INCHES MINIMUM AND 0.260 INCHES MAXIMUM FIRST SHOULDER IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: ASTM A153-60 ASSN STD SINGLE TREATMENT RESPONSE OVERALL
•
NONMACHINE NOMINAL THREAD DIAMETER: 0.250 INCHES IN
•
HEAD STYLE: SQUARE
•
MATERIAL: STEEL OVERALL
TECHNICAL CHARACTERISTICS (FLIS)
MATERIAL DOCUMENT AND CLASSIFICATIONFF-B-561,GRADE B FED SPEC SINGLE MATERIAL RESPONSE OVERALL
MINIMUM TENSILE STRENGTH55000 POUNDS PER SQUARE INCH LBS
NONDEFINITIVE SPEC/STD DATA1 TYPE AND 1 STYLE AND B GRADE
SHOULDER DIAMETER0.237 INCHES MINIMUM AND 0.260 INCHES MAXIMUM FIRST SHOULDER IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONASTM A153-60 ASSN STD SINGLE TREATMENT RESPONSE OVERALL
NONMACHINE NOMINAL THREAD DIAMETER0.250 INCHES IN
HEAD STYLESQUARE
MATERIALSTEEL OVERALL
FASTENER LENGTH5.000 INCHES NOMINAL IN
HARDNESS RATING60.0 ROCKWELL C NOMINAL OVERALL
VERIFIED SUBSTITUTES & CROSS-REFERENCES 1
MS16992-511Interchangeable
Same NIIN cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is FF-B-561?
FF-B-561 is a SCREW,LAG.
What parts can replace FF-B-561?
There is 1 known substitute for FF-B-561: MS16992-511. Substitute compatibility should be verified for your specific system.
What is the NSN for FF-B-561?
FF-B-561 is cataloged in the Federal Logistics Information System (FLIS) under NSN 5305-00-009-1797. This indicates validated use in U.S. government and defense supply chains.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026