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51B581-4-9 — SCREW,CLOSE TOLERANCE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

51B581-4-9: SCREW,CLOSE TOLERANCE.

The SCREW,CLOSE TOLERANCE is a the manufacturer industrial component. Key specifications include material: STEEL COMP 4340 OR STEEL COMP 4140 OR STEEL COMP 8740 OVERALL, head_style: FLAT COUNTERSUNK, grip_length: 0.552 INCHES MINIMUM AND 0.572 INCHES MAXIMUM IN, thread_class: 3A A, grip_diameter: 0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN, head_diameter: 0.390 INCHES MINIMUM AND 0.395 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5305-00-548-5077, 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
51B581-4-9
NSN: 5305-00-548-5077
FSC: 5305 — Screws
CAGE: 76823 — NORTHROP GRUMMAN SYSTEMS CORPORATION DBA NORTHROP GRUMMAN IS DIV NORTHROP GRUMMAN AERONAUTICS SYSTEMS (USA)
SPECIFICATIONS
materialSTEEL COMP 4340 OR STEEL COMP 4140 OR STEEL COMP 8740 OVERALL
head_styleFLAT COUNTERSUNK
grip_length0.552 INCHES MINIMUM AND 0.572 INCHES MAXIMUM IN
thread_class3A A
grip_diameter0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN
head_diameter0.390 INCHES MINIMUM AND 0.395 INCHES MAXIMUM IN
thread_length0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN
surface_finish32.0 MICROINCHES GRIP
fastener_length0.862 INCHES MINIMUM AND 0.909 INCHES MAXIMUM IN
hardness_rating39.0 ROCKWELL C MINIMUM AND 43.0 ROCKWELL C MAXIMUM OVERALL
thread_directionRIGHT-HAND
countersink_angle100.0 DEGREES NOMINAL
NSN5305-00-548-5077
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: 51B581-4-9 · 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
•
SURFACE FINISH: 32.0 MICROINCHES GRIP
•
FASTENER LENGTH: 0.862 INCHES MINIMUM AND 0.909 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
•
SHANK UNTHREADED HOLE DIAMETER: 0.076 INCHES NOMINAL FIRST HOLE IN
•
NOMINAL THREAD DIAMETER: 0.250 INCHES IN
•
HEAD STYLE: FLAT COUNTERSUNK
TECHNICAL CHARACTERISTICS
SURFACE FINISH32.0 MICROINCHES GRIP
FASTENER LENGTH0.862 INCHES MINIMUM AND 0.909 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
THREAD LENGTH0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN
HARDNESS RATING39.0 ROCKWELL C MINIMUM AND 43.0 ROCKWELL C MAXIMUM OVERALL
SHANK UNTHREADED HOLE DIAMETER0.076 INCHES NOMINAL FIRST HOLE IN
NOMINAL THREAD DIAMETER0.250 INCHES IN
HEAD STYLEFLAT COUNTERSUNK
THREAD DIRECTIONRIGHT-HAND
SPECIFICATION/STANDARD DATA76823-51B581 MANUFACTURERS STANDARD
OTHER ITEMS IN FSC 5305 — Screws
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5305-00-001-5016 5305-00-001-9160 5305-00-001-9629 5305-00-001-9742 5305-00-001-9768 5305-00-003-4306 5305-00-003-6694 5305-00-003-6753
SUBSTITUTES & CROSS-REFERENCES 1
51B581-4-9HSame NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Insurance item — stocked against contingency demandNo demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is 51B581-4-9?
51B581-4-9 is a SCREW,CLOSE TOLERANCE.
What parts can replace 51B581-4-9?
There is 1 known substitute for 51B581-4-9: 51B581-4-9H. Substitute compatibility should be verified for your specific system.
What is the NSN for 51B581-4-9?
51B581-4-9 is cataloged in the U.S. Government catalog under NSN 5305-00-548-5077. This indicates validated use in U.S. government and defense supply chains.
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✓ PartsTable — the parts reference. Every fact cited to its source.
PartsTable Design LLC · partstable.com
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.
PartsTable commercial catalog: edition Unified commercial catalog snapshot through 2026-09-28, edition date not on file, retrieved 2026-09-28.