PartsTable
Technical Data Sheet
Download PDF

KFN668-4 — NUT,SELF-LOCKING,EXTENDED WASHER

✓ Government record, cited
— · NUT WASHER
PRODUCT OVERVIEW

KFN668-4: NUT,SELF-LOCKING,EXTENDED WASHER.

NUT,SELF-LOCKING,EXTENDED WASHER. Key specifications include material: IRON ALLOY 660 OVERALL, nut_style: HEXAGON, lubrication: DRY FILM LUBRICANT, thread_class: 3B, thread_series: UNIFIED NATIONAL JOINT FINE (UNJF), overall_height: 0.340 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5310-01-306-9048, 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
KFN668-4
NSN: 5310-01-306-9048
FSC: 5310 — Nuts and Washers
CAGE: 56878 — SPS TECHNOLOGIES, LLC DBA PB FASTENERS (USA)
SPECIFICATIONS
materialIRON ALLOY 660 OVERALL
nut_styleHEXAGON
lubricationDRY FILM LUBRICANT
thread_class3B
thread_seriesUNIFIED NATIONAL JOINT FINE (UNJF)
overall_height0.340 INCHES MAXIMUM IN
locking_featurePREVAILING TORQUE ALL METAL DESIGN
special_featuresYELLOW IDENTIFICATION ON OUTSIDE OF NUT
thread_directionRIGHT-HAND
surface_treatmentPASSIVATE OVERALL
width_across_flats0.305 INCHES MINIMUM AND 0.313 INCHES MAXIMUM IN
nominal_thread_size0.250 INCHES IN
NSN5310-01-306-9048
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: KFN668-4 · 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: DRY FILM LUBRICANT
•
WASHER OUTSIDE DIAMETER: 0.425 INCHES MAXIMUM IN
•
WIDTH ACROSS FLATS: 0.305 INCHES MINIMUM AND 0.313 INCHES MAXIMUM IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: QQ-P-35 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
•
THREAD SERIES: UNIFIED NATIONAL JOINT FINE (UNJF)
•
MATERIAL DOCUMENT AND CLASSIFICATION: AMS 5643 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
•
NUT COUNTERBORE DEPTH: 0.107 INCHES MINIMUM AND 0.117 INCHES MAXIMUM WASHER IN
TECHNICAL CHARACTERISTICS
LUBRICATIONDRY FILM LUBRICANT
OVERALL HEIGHT0.340 INCHES MAXIMUM IN
WASHER OUTSIDE DIAMETER0.425 INCHES MAXIMUM IN
WIDTH ACROSS FLATS0.305 INCHES MINIMUM AND 0.313 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-35 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
THREAD SERIESUNIFIED NATIONAL JOINT FINE (UNJF)
MATERIAL DOCUMENT AND CLASSIFICATIONAMS 5643 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
NUT COUNTERBORE DEPTH0.107 INCHES MINIMUM AND 0.117 INCHES MAXIMUM WASHER IN
THREAD DIRECTIONRIGHT-HAND
NOMINAL THREAD SIZE0.250 INCHES IN
OTHER ITEMS IN FSC 5310 — Nuts and Washers
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5310-00-000-0040 5310-00-000-0077 5310-00-000-0079 5310-00-000-1146 5310-00-000-3815 5310-00-000-4532 5310-00-000-4540
SUBSTITUTES & CROSS-REFERENCES 5
BH00620M4Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
KFN517DL4Reference document
Same NSN cross-reference
Reference document — Secondary reference
KFN511DL4Reference document
Same NSN cross-reference
Reference document — Advisory reference — outside the item-of-supply concept
LE114-0031-0004Reference document
Same NSN cross-reference
Reference document — Vendor item drawing reference
03A136-4LSame NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Insurance item — stocked against contingency demandNo demilitarization required
Ready to buy KFN668-4?
Compare prices from verified sellers on eBay
Buy on eBay →
As an eBay Partner, PartsTable may earn a commission. Your price is not affected.
FREQUENTLY ASKED QUESTIONS
What is KFN668-4?
KFN668-4 is a NUT,SELF-LOCKING,EXTENDED WASHER.
What parts can replace KFN668-4?
There are 5 known substitutes for KFN668-4: BH00620M4, KFN517DL4, KFN511DL4 and 2 more. Substitute compatibility should be verified for your specific system.
What is the NSN for KFN668-4?
KFN668-4 is cataloged in the U.S. Government catalog under NSN 5310-01-306-9048. This indicates validated use in U.S. government and defense supply chains.
Community Feedback
Leave a Comment
Comments are reviewed before appearing. You will receive an email to verify before your comment appears.

Request a Quote — KFN668-4

✓ 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.