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PartsTable / COMPONENT / 999-78-3-9
999-78-3-9 ✓ 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,PLAIN,HEXAGON is a the manufacturer industrial component. Key specifications include material: NICKEL ALLOY OVERALL, nut_style: HEXAGON, nut_height: 0.375 INCHES NOMINAL IN, thread_class: 2B, thread_series: UNIFIED NATIONAL COARSE (UNC), thread_direction: RIGHT-HAND. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5310-01-521-1020, 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
999-78-3-9
NSN: 5310-01-521-1020
FSC: 5310
CAGE: 30263 — PIMA VALVE, LLC (USA)
SPECIFICATIONS
materialNICKEL ALLOY OVERALL
nut_styleHEXAGON
nut_height0.375 INCHES NOMINAL IN
thread_class2B
thread_seriesUNIFIED NATIONAL COARSE (UNC)
thread_directionRIGHT-HAND
width_across_flats1.063 INCHES NOMINAL IN
nominal_thread_size0.675 INCHES IN
bearing_surface_typeFLAT
end_item_identificationSWING CHECK VALVE
thread_quantity_per_inch11
material_document_and_classificationASTM-B164-2003 ASSN STD 1ST MATERIAL RESPONSE OVERALL
NSN5310-01-521-1020
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: 999-78-3-9 · 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: NICKEL ALLOY OVERALL
•
BEARING SURFACE TYPE: FLAT
•
MATERIAL DOCUMENT AND CLASSIFICATION: ASTM-B164-2003 ASSN STD 1ST MATERIAL RESPONSE OVERALL
•
NOMINAL THREAD SIZE: 0.675 INCHES IN
•
THREAD SERIES: UNIFIED NATIONAL COARSE (UNC)
•
THREAD CLASS: 2B
•
NUT HEIGHT: 0.375 INCHES NOMINAL IN
TECHNICAL CHARACTERISTICS (FLIS)
END ITEM IDENTIFICATIONSWING CHECK VALVE
MATERIALNICKEL ALLOY OVERALL
BEARING SURFACE TYPEFLAT
MATERIAL DOCUMENT AND CLASSIFICATIONASTM-B164-2003 ASSN STD 1ST MATERIAL RESPONSE OVERALL
NOMINAL THREAD SIZE0.675 INCHES IN
THREAD SERIESUNIFIED NATIONAL COARSE (UNC)
THREAD CLASS2B
NUT HEIGHT0.375 INCHES NOMINAL IN
NUT STYLEHEXAGON
WIDTH ACROSS FLATS1.063 INCHES NOMINAL IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 19
5000-4824-1385637Interchangeable
interchangeable cross-reference
interchangeable
1385637-5-250FInterchangeable
interchangeable cross-reference
interchangeable
5021B 5IN 10115Interchangeable
interchangeable cross-reference
interchangeable
810-1385637-8Interchangeable
interchangeable cross-reference
interchangeable
803-1385637-08Interchangeable
interchangeable cross-reference
interchangeable
S4824-1385637Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is 999-78-3-9?
999-78-3-9 is a NUT,PLAIN,HEXAGON.
What parts can replace 999-78-3-9?
There are 19 known substitutes for 999-78-3-9: 5000-4824-1385637, 1385637-5-250F, 5021B 5IN 10115 and 16 more. Substitute compatibility should be verified for your specific system.
What is the NSN for 999-78-3-9?
999-78-3-9 is cataloged in the Federal Logistics Information System (FLIS) under NSN 5310-01-521-1020. 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