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A51B21644-21 — WASHER,RECESSED

✓ Government record, cited
— · NUT WASHER
PRODUCT OVERVIEW

A51B21644-21: WASHER,RECESSED.

The WASHER,RECESSED is a the manufacturer industrial component. Key specifications include material: STEEL OVERALL, recess_angle: 100.0 DEGREES NOMINAL, hole_diameter: 0.514 INCHES MINIMUM AND 0.523 INCHES MAXIMUM IN, surface_finish: 125.0 MICROINCHES ALL SURFACES, hardness_rating: 46.0 ROCKWELL C MINIMUM AND 49.0 ROCKWELL C MAXIMUM, recess_diameter: 1.014 INCHES NOMINAL IN. This part is cataloged in the U.S.

Government catalog under NSN 5310-01-076-9428, 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
A51B21644-21
NSN: 5310-01-076-9428
FSC: 5310 — Nuts and Washers
CAGE: 79RG9 — NORTHROP GRUMMAN SYSTEMS CORPORATION (USA)
SPECIFICATIONS
materialSTEEL OVERALL
recess_angle100.0 DEGREES NOMINAL
hole_diameter0.514 INCHES MINIMUM AND 0.523 INCHES MAXIMUM IN
surface_finish125.0 MICROINCHES ALL SURFACES
hardness_rating46.0 ROCKWELL C MINIMUM AND 49.0 ROCKWELL C MAXIMUM
recess_diameter1.014 INCHES NOMINAL IN
outside_diameter1.550 INCHES NOMINAL IN
special_featuresTOP SURFACE CHAMFERED 0.200 IN. BY 45 DEG IN
style_designatorRECESSED
surface_treatmentCADMIUM OVERALL
material_thickness0.270 INCHES NOMINAL IN
material_document_and_classificationG-1013,COMP D6AC MFR REF SINGLE MATERIAL RESPONSE OVERALL
NSN5310-01-076-9428
COMPONENT DIAGRAM
NUT & WASHER — GRADE MATCHING REQUIRED Hex NUT CROSS-SECTION WASHER OD: — SIZE: — MATERIAL: — PN: A51B21644-21 · 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 FINISH: 125.0 MICROINCHES ALL SURFACES
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: MIL-C-8837,TYPE 2,CLASS 1 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
•
HARDNESS RATING: 46.0 ROCKWELL C MINIMUM AND 49.0 ROCKWELL C MAXIMUM
•
STYLE DESIGNATOR: RECESSED
•
MATERIAL DOCUMENT AND CLASSIFICATION: G-1013,COMP D6AC MFR REF SINGLE MATERIAL RESPONSE OVERALL
•
OUTSIDE DIAMETER: 1.550 INCHES NOMINAL IN
•
MATERIAL THICKNESS: 0.270 INCHES NOMINAL IN
•
RECESS DIAMETER: 1.014 INCHES NOMINAL IN
TECHNICAL CHARACTERISTICS
SURFACE FINISH125.0 MICROINCHES ALL SURFACES
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONMIL-C-8837,TYPE 2,CLASS 1 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
HARDNESS RATING46.0 ROCKWELL C MINIMUM AND 49.0 ROCKWELL C MAXIMUM
STYLE DESIGNATORRECESSED
MATERIAL DOCUMENT AND CLASSIFICATIONG-1013,COMP D6AC MFR REF SINGLE MATERIAL RESPONSE OVERALL
OUTSIDE DIAMETER1.550 INCHES NOMINAL IN
MATERIAL THICKNESS0.270 INCHES NOMINAL IN
RECESS DIAMETER1.014 INCHES NOMINAL IN
SPECIAL FEATURESTOP SURFACE CHAMFERED 0.200 IN. BY 45 DEG IN
SURFACE TREATMENTCADMIUM OVERALL
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

No substitute or cross-reference records for this part.

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 A51B21644-21?
A51B21644-21 is a WASHER,RECESSED.
What is the NSN for A51B21644-21?
A51B21644-21 is cataloged in the U.S. Government catalog under NSN 5310-01-076-9428. 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.