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51B581-4-4 — SCREW,CLOSE TOLERANCE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

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

The SCREW,CLOSE TOLERANCE is a the manufacturer industrial component. Key specifications include material: STEEL COMP E4340 OR STEEL COMP 4340 OR STEEL COMP 6150 OVERALL, head_style: FLAT COUNTERSUNK, grip_length: 0.240 INCHES MINIMUM AND 0.260 INCHES MAXIMUM IN, thread_class: 3A A, grip_diameter: 0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN, head_diameter: 0.394 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5305-00-004-5114, 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
51B581-4-4
NSN: 5305-00-004-5114
FSC: 5305 — Screws
CAGE: 79U29 — NORTHROP GRUMMAN SYSTEMS CORPORATION (USA)
SPECIFICATIONS
materialSTEEL COMP E4340 OR STEEL COMP 4340 OR STEEL COMP 6150 OVERALL
head_styleFLAT COUNTERSUNK
grip_length0.240 INCHES MINIMUM AND 0.260 INCHES MAXIMUM IN
thread_class3A A
grip_diameter0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN
head_diameter0.394 INCHES MAXIMUM IN
thread_length0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN
surface_finish32.0 MICROINCHES GRIP
fastener_length0.550 INCHES MINIMUM AND 0.597 INCHES MAXIMUM IN
thread_directionRIGHT-HAND
countersink_angle99.5 DEGREES MINIMUM AND 100.5 DEGREES MAXIMUM
surface_treatmentCADMIUM AND CHROMATE OVERALL
NSN5305-00-004-5114
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: 51B581-4-4 · 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: 0.550 INCHES MINIMUM AND 0.597 INCHES MAXIMUM IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: QQ-P-416,TY 2,CL 3 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
•
THREAD LENGTH: 0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN
•
NOMINAL THREAD DIAMETER: 0.250 INCHES IN
•
HEAD STYLE: FLAT COUNTERSUNK
•
THREAD DIRECTION: RIGHT-HAND
•
GRIP LENGTH: 0.240 INCHES MINIMUM AND 0.260 INCHES MAXIMUM IN
TECHNICAL CHARACTERISTICS
SURFACE FINISH32.0 MICROINCHES GRIP
FASTENER LENGTH0.550 INCHES MINIMUM AND 0.597 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-416,TY 2,CL 3 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
THREAD LENGTH0.290 INCHES MINIMUM AND 0.357 INCHES MAXIMUM IN
NOMINAL THREAD DIAMETER0.250 INCHES IN
HEAD STYLEFLAT COUNTERSUNK
THREAD DIRECTIONRIGHT-HAND
GRIP LENGTH0.240 INCHES MINIMUM AND 0.260 INCHES MAXIMUM IN
GRIP DIAMETER0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN
SURFACE TREATMENTCADMIUM AND CHROMATE OVERALL
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

No substitute or cross-reference records for this part.

LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Normally procured from the manufacturer (OEM)No demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is 51B581-4-4?
51B581-4-4 is a SCREW,CLOSE TOLERANCE.
What is the NSN for 51B581-4-4?
51B581-4-4 is cataloged in the U.S. Government catalog under NSN 5305-00-004-5114. 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.