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PartsTable / COMPONENT / 3M221-5
3M221-5 ✓ Verified by PartsTable
— · NUT WASHER
WHAT YOU NEED TO KNOW
Match nut grade to bolt grade for full strength Lock nuts prevent loosening under vibration
Don't mix grades — weakens the joint
PRODUCT OVERVIEW

NUT,SELF-LOCKING,EXTENDED WASHER. Key specifications include material: STEEL OVERALL, nut_style: DOUBLE HEXAGON, lubrication: DRY FILM LUBRICANT, temp_rating: 450.0 FAHRENHEIT NOMINAL DEGF, thread_class: 3B, thread_series: UNIFIED NATIONAL JOINT FINE (UNJF). This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5310-00-723-3870, 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
3M221-5
NSN: 5310-00-723-3870
FSC: 5310
CAGE: 76301 — THE BOEING COMPANY DIV DEFENSE (USA)
SPECIFICATIONS
materialSTEEL OVERALL
nut_styleDOUBLE HEXAGON
lubricationDRY FILM LUBRICANT
temp_rating450.0 FAHRENHEIT NOMINAL DEGF
thread_class3B
thread_seriesUNIFIED NATIONAL JOINT FINE (UNJF)
overall_height0.360 INCHES MAXIMUM IN
locking_featurePREVAILING TORQUE ALL METAL DESIGN
thread_directionRIGHT-HAND
washer_thickness0.048 INCHES NOMINAL IN
surface_treatmentCADMIUM OVERALL
width_across_flats0.367 INCHES MINIMUM AND 0.376 INCHES MAXIMUM IN
NSN5310-00-723-3870
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: 3M221-5 · OEM ⚠ VERIFY BEFORE ORDERING Grade matters for torque spec — don't mix grades. A Grade 5 nut on a Grade 8 bolt weakens the joint. Lock nuts, wing nuts, and castle nuts are NOT interchangeable with standard hex ✓ BROKER TIP Match nut to bolt thread class and material. Stainless bolt + zinc nut = galvanic corrosion. Always verify finish matches (plain, zinc, hot-dip galvanized) PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
LOCKING FEATURE: PREVAILING TORQUE ALL METAL DESIGN
•
NOMINAL THREAD SIZE: 0.312 INCHES IN
•
THREAD DIRECTION: RIGHT-HAND
•
TEMP RATING: 450.0 FAHRENHEIT NOMINAL DEGF
•
WIDTH ACROSS FLATS: 0.367 INCHES MINIMUM AND 0.376 INCHES MAXIMUM IN
•
MATERIAL: STEEL OVERALL
•
THREAD QUANTITY PER INCH: 24
•
SURFACE TREATMENT: CADMIUM OVERALL
TECHNICAL CHARACTERISTICS (FLIS)
LOCKING FEATUREPREVAILING TORQUE ALL METAL DESIGN
NOMINAL THREAD SIZE0.312 INCHES IN
THREAD DIRECTIONRIGHT-HAND
TEMP RATING450.0 FAHRENHEIT NOMINAL DEGF
WIDTH ACROSS FLATS0.367 INCHES MINIMUM AND 0.376 INCHES MAXIMUM IN
MATERIALSTEEL OVERALL
THREAD QUANTITY PER INCH24
SURFACE TREATMENTCADMIUM OVERALL
NUT STYLEDOUBLE HEXAGON
WASHER OUTSIDE DIAMETER0.568 INCHES MAXIMUM IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 14
VK152Interchangeable
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760039M1Interchangeable
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VR78Interchangeable
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H2-35Interchangeable
interchangeable cross-reference
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91-4-19-41 SDBInterchangeable
interchangeable cross-reference
interchangeable
35Interchangeable
Pago tarjeta de credito
interchangeable
LIFECYCLE
StatusCANCELLED
Availability—
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is 3M221-5?
3M221-5 is a NUT,SELF-LOCKING,EXTENDED WASHER.
What parts can replace 3M221-5?
There are 14 known substitutes for 3M221-5: VK152, 760039M1, VR78 and 11 more. Substitute compatibility should be verified for your specific system.
Is 3M221-5 still available?
3M221-5 is currently cancelled.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026