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MB251-3-5 — BOLT,CLOSE TOLERANCE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

MB251-3-5: BOLT,CLOSE TOLERANCE.

The BOLT,CLOSE TOLERANCE is a the manufacturer industrial component. Key specifications include material: TITANIUM ALLOY UNS R56400 OVERALL, head_style: HEXAGON, grip_length: 0.302 INCHES MINIMUM AND 0.322 INCHES MAXIMUM IN, head_height: 0.110 INCHES MINIMUM AND 0.125 INCHES MAXIMUM IN, thread_class: 3A A, grip_diameter: 0.1885 INCHES MINIMUM AND 0.1895 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5306-01-256-6881, 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
MB251-3-5
NSN: 5306-01-256-6881
FSC: 5306 — Bolts
CAGE: L4528 — LISI AEROSPACE CANADA CORP DIV HI SHEAR HOLDINGS INC (CAN)
SPECIFICATIONS
materialTITANIUM ALLOY UNS R56400 OVERALL
head_styleHEXAGON
grip_length0.302 INCHES MINIMUM AND 0.322 INCHES MAXIMUM IN
head_height0.110 INCHES MINIMUM AND 0.125 INCHES MAXIMUM IN
thread_class3A A
grip_diameter0.1885 INCHES MINIMUM AND 0.1895 INCHES MAXIMUM IN
thread_length0.313 INCHES MINIMUM AND 0.363 INCHES MAXIMUM IN
surface_finish16.0 MICROINCHES THREADS
fastener_length0.635 INCHES MINIMUM AND 0.665 INCHES MAXIMUM IN
thread_directionRIGHT-HAND
surface_treatmentALUMINUM OVERALL
width_between_flats0.367 INCHES MINIMUM AND 0.376 INCHES MAXIMUM IN
NSN5306-01-256-6881
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: MB251-3-5 · 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: 63.0 MICROINCHES GRIP
•
HEAD HEIGHT: 0.110 INCHES MINIMUM AND 0.125 INCHES MAXIMUM IN
•
FASTENER LENGTH: 0.635 INCHES MINIMUM AND 0.665 INCHES MAXIMUM IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: MIL-C-83488,TYPE 2 CLASS 3 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
•
THREAD LENGTH: 0.313 INCHES MINIMUM AND 0.363 INCHES MAXIMUM IN
•
MATERIAL DOCUMENT AND CLASSIFICATION: AMS4967 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
TECHNICAL CHARACTERISTICS
SURFACE FINISH63.0 MICROINCHES GRIP
SURFACE FINISH63.0 MICROINCHES BEARING SURFACE OF HEAD
SURFACE FINISH16.0 MICROINCHES THREADS
HEAD HEIGHT0.110 INCHES MINIMUM AND 0.125 INCHES MAXIMUM IN
FASTENER LENGTH0.635 INCHES MINIMUM AND 0.665 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONMIL-C-83488,TYPE 2 CLASS 3 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
THREAD LENGTH0.313 INCHES MINIMUM AND 0.363 INCHES MAXIMUM IN
MATERIAL DOCUMENT AND CLASSIFICATIONAMS4967 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
NOMINAL THREAD DIAMETER0.190 INCHES IN
HEAD STYLEHEXAGON
SUBSTITUTES & CROSS-REFERENCES 5
ST3M7Reference document
Same NSN cross-reference
Reference document — Secondary reference
ST3M731-3-5Reference document
Same NSN cross-reference
Reference document — Secondary reference
VS3207-3-5Reference document
Same NSN cross-reference
Reference document — Secondary reference
SC2663-3-5Reference document
Same NSN cross-reference
Reference document — Secondary reference
PBF1264-3-5Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
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 MB251-3-5?
MB251-3-5 is a BOLT,CLOSE TOLERANCE.
What parts can replace MB251-3-5?
There are 5 known substitutes for MB251-3-5: ST3M7, ST3M731-3-5, VS3207-3-5 and 2 more. Substitute compatibility should be verified for your specific system.
What is the NSN for MB251-3-5?
MB251-3-5 is cataloged in the U.S. Government catalog under NSN 5306-01-256-6881. 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.