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KFN668-08 — NUT,SELF-LOCKING,EXTENDED WASHER

✓ Government record, cited
— · NUT WASHER
PRODUCT OVERVIEW

KFN668-08: NUT,SELF-LOCKING,EXTENDED WASHER.

NUT,SELF-LOCKING,EXTENDED WASHER. Key specifications include material: STEEL COMP 630 OVERALL, nut_style: HEXAGON, thread_class: 3B, thread_series: UNIFIED NATIONAL JOINT FINE (UNJF), overall_height: 0.270 INCHES MAXIMUM IN, locking_feature: PREVAILING TORQUE ALL METAL DESIGN. This part is cataloged in the U.S.

Government catalog under NSN 5310-01-660-3133, 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
KFN668-08
NSN: 5310-01-660-3133
FSC: 5310 — Nuts and Washers
CAGE: 15653 — HOWMET GLOBAL FASTENING SYSTEMS INC (USA)
SPECIFICATIONS
materialSTEEL COMP 630 OVERALL
nut_styleHEXAGON
thread_class3B
thread_seriesUNIFIED NATIONAL JOINT FINE (UNJF)
overall_height0.270 INCHES MAXIMUM IN
locking_featurePREVAILING TORQUE ALL METAL DESIGN
thread_directionRIGHT-HAND
washer_thickness0.102 INCHES MINIMUM AND 0.112 INCHES MAXIMUM IN
surface_treatmentPASSIVATE OVERALL
width_across_flats0.212 INCHES MINIMUM AND 0.220 INCHES MAXIMUM IN
nominal_thread_size0.164 INCHES IN
counterbore_diameter0.198 INCHES MINIMUM AND 0.202 INCHES MAXIMUM WASHER IN
NSN5310-01-660-3133
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: KFN668-08 · 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
•
WASHER OUTSIDE DIAMETER: 0.290 INCHES MAXIMUM IN
•
WIDTH ACROSS FLATS: 0.212 INCHES MINIMUM AND 0.220 INCHES MAXIMUM IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: QQ-P-35 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
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THREAD SERIES: UNIFIED NATIONAL JOINT FINE (UNJF)
•
WASHER THICKNESS: 0.102 INCHES MINIMUM AND 0.112 INCHES MAXIMUM IN
•
MATERIAL DOCUMENT AND CLASSIFICATION: AMS 5643 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
•
THREAD DIRECTION: RIGHT-HAND
TECHNICAL CHARACTERISTICS
OVERALL HEIGHT0.270 INCHES MAXIMUM IN
WASHER OUTSIDE DIAMETER0.290 INCHES MAXIMUM IN
WIDTH ACROSS FLATS0.212 INCHES MINIMUM AND 0.220 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-35 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
THREAD SERIESUNIFIED NATIONAL JOINT FINE (UNJF)
WASHER THICKNESS0.102 INCHES MINIMUM AND 0.112 INCHES MAXIMUM IN
MATERIAL DOCUMENT AND CLASSIFICATIONAMS 5643 ASSN STD SINGLE MATERIAL RESPONSE OVERALL
THREAD DIRECTIONRIGHT-HAND
NOMINAL THREAD SIZE0.164 INCHES IN
COUNTERBORE DIAMETER0.198 INCHES MINIMUM AND 0.202 INCHES MAXIMUM WASHER 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 1
LE114-0031-0002Reference document
Same NSN cross-reference
Reference document — Vendor item drawing reference
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Normally procured from the manufacturer (OEM)No demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is KFN668-08?
KFN668-08 is a NUT,SELF-LOCKING,EXTENDED WASHER.
What parts can replace KFN668-08?
There is 1 known substitute for KFN668-08: LE114-0031-0002. Substitute compatibility should be verified for your specific system.
What is the NSN for KFN668-08?
KFN668-08 is cataloged in the U.S. Government catalog under NSN 5310-01-660-3133. This indicates validated use in U.S. government and defense supply chains.
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✓ 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.