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50FK420 ✓ 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,SLOTTED,HEXAGON. Key specifications include material: STEEL COMP 302 OR STEEL COMP 303 OVERALL, nut_style: HEXAGON, nut_height: 0.199 INCHES NOMINAL IN, thread_class: 2B, thread_series: UNIFIED NATIONAL COARSE (UNC), locking_feature: FREE-RUNNING ALL METAL DESIGN. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5310-00-004-1490, 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
50FK420
NSN: 5310-00-004-1490
FSC: 5310
CAGE: 56878 — SPS TECHNOLOGIES, LLC DBA PB FASTENERS (USA)
SPECIFICATIONS
materialSTEEL COMP 302 OR STEEL COMP 303 OVERALL
nut_styleHEXAGON
nut_height0.199 INCHES NOMINAL IN
thread_class2B
thread_seriesUNIFIED NATIONAL COARSE (UNC)
locking_featureFREE-RUNNING ALL METAL DESIGN
thread_directionRIGHT-HAND
width_across_flats0.4345 INCHES NOMINAL IN
nominal_thread_size0.250 INCHES IN
bearing_surface_typeFLAT
thread_quantity_per_inch20
material_document_and_classificationASTM A582 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
NSN5310-00-004-1490
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: 50FK420 · 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
•
MATERIAL: STEEL CORROSION RESISTING OVERALL
•
NUT HEIGHT: 0.189 INCHES MINIMUM AND 0.209 INCHES MAXIMUM IN
•
TEST DATA DOCUMENT: 81349-MIL-P-23199 SPECIFICATION (INCLUDES ENGINEERING TYPE BULLETINS, BROCHURES,ETC., THAT REFLECT SPECIFICATION TYPE DATA IN SPECIFICATION FORMAT; EXCLUDES COMMERCIAL CATALOGS, INDUSTRY DIRECTORIES, AND SIMILAR TRADE PUBLICATIONS, REFLECTING GENERAL TYPE DATA ON CERTAIN ENVIRONMENTAL AND PERFORMANCE REQUIREMENTS AND TEST CONDITIONS THAT ARE SHOWN AS "TYPICAL", "AVERAGE", "NOMINAL", ETC.).
•
THREAD DIRECTION: RIGHT-HAND
•
BEARING SURFACE TYPE: CHAMFERED
•
NOMINAL THREAD SIZE: 0.250 INCHES IN
•
WIDTH ACROSS FLATS: 0.430 INCHES MINIMUM AND 0.439 INCHES MAXIMUM IN
•
SURFACE TREATMENT: PASSIVATE OVERALL
TECHNICAL CHARACTERISTICS (FLIS)
MATERIALSTEEL CORROSION RESISTING OVERALL
NUT HEIGHT0.189 INCHES MINIMUM AND 0.209 INCHES MAXIMUM IN
TEST DATA DOCUMENT81349-MIL-P-23199 SPECIFICATION (INCLUDES ENGINEERING TYPE BULLETINS, BROCHURES,ETC., THAT REFLECT SPECIFICATION TYPE DATA IN SPECIFICATION FORMAT; EXCLUDES COMMERCIAL CATALOGS, INDUSTRY DIRECTORIES, AND SIMILAR TRADE PUBLICATIONS, REFLECTING GENERAL TYPE DATA ON CERTAIN ENVIRONMENTAL AND PERFORMANCE REQUIREMENTS AND TEST CONDITIONS THAT ARE SHOWN AS "TYPICAL", "AVERAGE", "NOMINAL", ETC.).
THREAD DIRECTIONRIGHT-HAND
BEARING SURFACE TYPECHAMFERED
NOMINAL THREAD SIZE0.250 INCHES IN
WIDTH ACROSS FLATS0.430 INCHES MINIMUM AND 0.439 INCHES MAXIMUM IN
SURFACE TREATMENTPASSIVATE OVERALL
SPECIAL TEST FEATURESSPECIAL QUALITY CONTROL TESTING
TEMP RATING800.0 FAHRENHEIT NOMINAL DEGF
VERIFIED SUBSTITUTES & CROSS-REFERENCES 3
50FK420Interchangeable
interchangeable cross-reference
interchangeable
80307Interchangeable
interchangeable cross-reference
interchangeable
12266953-2Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is 50FK420?
50FK420 is a NUT,SELF-LOCKING,SLOTTED,HEXAGON.
What parts can replace 50FK420?
There are 3 known substitutes for 50FK420: 50FK420, 80307, 12266953-2. Substitute compatibility should be verified for your specific system.
What is the NSN for 50FK420?
50FK420 is cataloged in the Federal Logistics Information System (FLIS) under NSN 5310-00-004-1490. This indicates validated use in U.S. government and defense supply chains.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026