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21FK813 ✓ 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

The NUT,SELF-LOCKING,HEXAGON is a the manufacturer industrial component. Key specifications include material: STEEL OVERALL, nut_style: HEXAGON, nut_height: 0.328 INCHES MAXIMUM IN, lubrication: SOLUBLE LUBRICANT, thread_class: 2B, thread_series: UNIFIED NATIONAL COARSE (UNC). This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5310-01-012-2684, 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
21FK813
NSN: 5310-01-012-2684
FSC: 5310
CAGE: 56878 — SPS TECHNOLOGIES, LLC DBA PB FASTENERS (USA)
SPECIFICATIONS
materialSTEEL OVERALL
nut_styleHEXAGON
nut_height0.328 INCHES MAXIMUM IN
lubricationSOLUBLE LUBRICANT
thread_class2B
thread_seriesUNIFIED NATIONAL COARSE (UNC)
locking_featurePREVAILING TORQUE ALL METAL DESIGN
thread_directionRIGHT-HAND
surface_treatmentCADMIUM OVERALL
width_across_flats0.741 INCHES MINIMUM AND 0.752 INCHES MAXIMUM IN
nominal_thread_size0.500 INCHES IN
bearing_surface_typeCHAMFERED
NSN5310-01-012-2684
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: 21FK813 · 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
•
LUBRICATION: SOLUBLE LUBRICANT
•
THREAD DIRECTION: RIGHT-HAND
•
SURFACE TREATMENT: CADMIUM OVERALL
•
NOMINAL THREAD SIZE: 0.500 INCHES IN
•
THREAD SERIES: UNIFIED NATIONAL COARSE (UNC)
•
BEARING SURFACE TYPE: CHAMFERED
•
THREAD QUANTITY PER INCH: 13
•
MATERIAL: STEEL OVERALL
TECHNICAL CHARACTERISTICS (FLIS)
LUBRICATIONSOLUBLE LUBRICANT
THREAD DIRECTIONRIGHT-HAND
SURFACE TREATMENTCADMIUM OVERALL
NOMINAL THREAD SIZE0.500 INCHES IN
THREAD SERIESUNIFIED NATIONAL COARSE (UNC)
BEARING SURFACE TYPECHAMFERED
THREAD QUANTITY PER INCH13
MATERIALSTEEL OVERALL
NUT STYLEHEXAGON
NUT HEIGHT0.328 INCHES MAXIMUM IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 16
80111-00Interchangeable
interchangeable cross-reference
interchangeable
80111Interchangeable
interchangeable cross-reference
interchangeable
X1-10Interchangeable
interchangeable cross-reference
interchangeable
JIC-1/2Interchangeable
interchangeable cross-reference
interchangeable
47002Interchangeable
interchangeable cross-reference
interchangeable
EFInterchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusCANCELLED
Availability—
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is 21FK813?
21FK813 is a NUT,SELF-LOCKING,HEXAGON.
What parts can replace 21FK813?
There are 16 known substitutes for 21FK813: 80111-00, 80111, X1-10 and 13 more. Substitute compatibility should be verified for your specific system.
Is 21FK813 still available?
21FK813 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