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721009663900 — WASHER,RECESSED

✓ Government record, cited
— · NUT WASHER
PRODUCT OVERVIEW

721009663900: WASHER,RECESSED.

The WASHER,RECESSED is a the manufacturer industrial component. Key specifications include material: STEEL COMP 4130 OVERALL, recess_angle: 90.0 DEGREES NOMINAL, hole_diameter: 0.251 INCHES MINIMUM AND 0.255 INCHES MAXIMUM IN, hardness_rating: 39.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM, recess_diameter: 0.340 INCHES MINIMUM AND 0.350 INCHES MAXIMUM IN, outside_diameter: 0.481 INCHES MINIMUM AND 0.491 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5310-01-008-6798, 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
721009663900
NSN: 5310-01-008-6798
FSC: 5310 — Nuts and Washers
CAGE: A1140 — LEONARDO SPA DIVISIONE SISTEMI DI DIFESA (ITA)
SPECIFICATIONS
materialSTEEL COMP 4130 OVERALL
recess_angle90.0 DEGREES NOMINAL
hole_diameter0.251 INCHES MINIMUM AND 0.255 INCHES MAXIMUM IN
hardness_rating39.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM
recess_diameter0.340 INCHES MINIMUM AND 0.350 INCHES MAXIMUM IN
outside_diameter0.481 INCHES MINIMUM AND 0.491 INCHES MAXIMUM IN
style_designatorRECESSED
surface_treatmentCADMIUM AND CHROMATE OVERALL
material_thickness0.067 INCHES MINIMUM AND 0.069 INCHES MAXIMUM IN
material_document_and_classificationMIL-S-6758 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-S-18729 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
surface_treatment_document_and_classificationQQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
NSN5310-01-008-6798
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: 721009663900 · 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
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
•
HARDNESS RATING: 39.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM
•
STYLE DESIGNATOR: RECESSED
•
MATERIAL DOCUMENT AND CLASSIFICATION: MIL-S-6758 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-S-18729 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
•
OUTSIDE DIAMETER: 0.481 INCHES MINIMUM AND 0.491 INCHES MAXIMUM IN
•
MATERIAL THICKNESS: 0.067 INCHES MINIMUM AND 0.069 INCHES MAXIMUM IN
•
RECESS DIAMETER: 0.340 INCHES MINIMUM AND 0.350 INCHES MAXIMUM IN
•
SURFACE TREATMENT: CADMIUM AND CHROMATE OVERALL
TECHNICAL CHARACTERISTICS
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
HARDNESS RATING39.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM
STYLE DESIGNATORRECESSED
MATERIAL DOCUMENT AND CLASSIFICATIONMIL-S-6758 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-S-18729 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
OUTSIDE DIAMETER0.481 INCHES MINIMUM AND 0.491 INCHES MAXIMUM IN
MATERIAL THICKNESS0.067 INCHES MINIMUM AND 0.069 INCHES MAXIMUM IN
RECESS DIAMETER0.340 INCHES MINIMUM AND 0.350 INCHES MAXIMUM IN
SURFACE TREATMENTCADMIUM AND CHROMATE OVERALL
MATERIALSTEEL COMP 4130 OVERALL
HOLE DIAMETER0.251 INCHES MINIMUM AND 0.255 INCHES MAXIMUM 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 3
10121940Reference document
Same NSN cross-reference
Reference document — Informative reference only
5310PL2129960Reference document
Same NSN cross-reference
Reference document — Informative reference only
MS21299-C4Reference document
Same NSN cross-reference
Reference document — Advisory reference — outside the item-of-supply concept
LIFECYCLE
NSN statusActive· U.S. Government catalog
No demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is 721009663900?
721009663900 is a WASHER,RECESSED.
What parts can replace 721009663900?
There are 3 known substitutes for 721009663900: 10121940, 5310PL2129960, MS21299-C4. Substitute compatibility should be verified for your specific system.
What is the NSN for 721009663900?
721009663900 is cataloged in the U.S. Government catalog under NSN 5310-01-008-6798. 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.