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C20645B3-4 — SCREW,CLOSE TOLERANCE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

C20645B3-4: SCREW,CLOSE TOLERANCE.

The SCREW,CLOSE TOLERANCE is a the manufacturer industrial component. Key specifications include material: STEEL OVERALL, head_style: FLAT COUNTERSUNK, grip_length: 0.250 INCHES NOMINAL IN, head_height: 0.049 INCHES NOMINAL IN, thread_class: 3A A, grip_diameter: 0.1885 INCHES MINIMUM AND 0.1895 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5305-01-692-5164, 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
C20645B3-4
NSN: 5305-01-692-5164
FSC: 5305 — Screws
CAGE: 81755 — LOCKHEED MARTIN CORPORATION DIV LOCKHEED MARTIN AERONAUTICS COMPANY (USA)
SPECIFICATIONS
materialSTEEL OVERALL
head_styleFLAT COUNTERSUNK
grip_length0.250 INCHES NOMINAL IN
head_height0.049 INCHES NOMINAL IN
thread_class3A A
grip_diameter0.1885 INCHES MINIMUM AND 0.1895 INCHES MAXIMUM IN
head_diameter0.258 INCHES MINIMUM AND 0.305 INCHES MAXIMUM IN
thread_length0.363 INCHES NOMINAL IN
surface_finish32.0 MICROINCHES OVERALL
fastener_length0.598 INCHES MINIMUM AND 0.628 INCHES MAXIMUM IN
hardness_rating46.0 ROCKWELL C MINIMUM AND 50.0 ROCKWELL C MAXIMUM OVERALL
thread_directionRIGHT-HAND
NSN5305-01-692-5164
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: C20645B3-4 · OEM ⚠ VERIFY BEFORE ORDERING Verify thread pitch before ordering — metric (M8×1.25) ≠ imperial (5/16-18). Wrong thread = wrong part. Grade/class stamped on bolt head determines tensile strength ✓ BROKER TIP Grade/class stamped on head determines tensile strength. Grade 8 > Grade 5 > Grade 2. Always confirm head marking matches specification requirement PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
SURFACE FINISH: 32.0 MICROINCHES OVERALL
•
HEAD HEIGHT: 0.049 INCHES NOMINAL IN
•
FASTENER LENGTH: 0.598 INCHES MINIMUM AND 0.628 INCHES MAXIMUM IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: ION VAPOR DEPOSITED ALUMINUM COATED PER MIL-DTL-83488,TY II,CL 3 MIL SPEC 1ST TREATMENT RESPONSE AND DRY FILM LUBRICANT PER MIL-PRF-46010(OR AS5272 TY I) APPLIED OVER ALUMINUM COATING MIL SPEC 2ND TREATMENT RESPONSE OVERALL
•
THREAD LENGTH: 0.363 INCHES NOMINAL IN
•
HARDNESS RATING: 46.0 ROCKWELL C MINIMUM AND 50.0 ROCKWELL C MAXIMUM OVERALL
•
MATERIAL DOCUMENT AND CLASSIFICATION: H11 ALLOY STEEL PER AMS6487 AEROSPACE MATERIAL SPEC STD SINGLE MATERIAL RESPONSE OVERALL
•
SINGLE SHEAR STRENGTH: ERR-060
TECHNICAL CHARACTERISTICS
SURFACE FINISH32.0 MICROINCHES OVERALL
HEAD HEIGHT0.049 INCHES NOMINAL IN
FASTENER LENGTH0.598 INCHES MINIMUM AND 0.628 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONION VAPOR DEPOSITED ALUMINUM COATED PER MIL-DTL-83488,TY II,CL 3 MIL SPEC 1ST TREATMENT RESPONSE AND DRY FILM LUBRICANT PER MIL-PRF-46010(OR AS5272 TY I) APPLIED OVER ALUMINUM COATING MIL SPEC 2ND TREATMENT RESPONSE OVERALL
THREAD LENGTH0.363 INCHES NOMINAL IN
HARDNESS RATING46.0 ROCKWELL C MINIMUM AND 50.0 ROCKWELL C MAXIMUM OVERALL
MATERIAL DOCUMENT AND CLASSIFICATIONH11 ALLOY STEEL PER AMS6487 AEROSPACE MATERIAL SPEC STD SINGLE MATERIAL RESPONSE OVERALL
SINGLE SHEAR STRENGTHERR-060
NOMINAL THREAD DIAMETER0.1900 INCHES IN
FEATURES PROVIDEDDRY FILM LUBRICANT
OTHER ITEMS IN FSC 5305 — Screws
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5305-00-001-5016 5305-00-001-9160 5305-00-001-9629 5305-00-001-9742 5305-00-001-9768 5305-00-003-4306 5305-00-003-6694 5305-00-003-6753
SUBSTITUTES & CROSS-REFERENCES 1
C20645Reference document
Same NSN cross-reference
Reference document — Drawing number reference only
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Insurance item — stocked against contingency demandNo demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is C20645B3-4?
C20645B3-4 is a SCREW,CLOSE TOLERANCE.
What parts can replace C20645B3-4?
There is 1 known substitute for C20645B3-4: C20645. Substitute compatibility should be verified for your specific system.
What is the NSN for C20645B3-4?
C20645B3-4 is cataloged in the U.S. Government catalog under NSN 5305-01-692-5164. 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.