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521397778 — SCREW,MACHINE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

521397778: SCREW,MACHINE.

The SCREW,MACHINE is a the manufacturer industrial component. Key specifications include head_style: FLAT COUNTERSUNK, thread_class: 2A A, head_diameter: 0.188 INCHES NOMINAL IN, thread_length: 0.219 INCHES MINIMUM IN, screw_material: STEEL, fastener_length: 0.250 INCHES NOMINAL IN. This part is cataloged in the U.S.

Government catalog under NSN 5305-00-754-4254, 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
521397778
NSN: 5305-00-754-4254
FSC: 5305 — Screws
CAGE: 57712 — TELEMECHANICS INC (USA)
SPECIFICATIONS
head_styleFLAT COUNTERSUNK
thread_class2A A
head_diameter0.188 INCHES NOMINAL IN
thread_length0.219 INCHES MINIMUM IN
screw_materialSTEEL
fastener_length0.250 INCHES NOMINAL IN
thread_directionRIGHT-HAND
countersink_angle90.0 DEGREES NOMINAL
internal_drive_styleSLOT
nominal_thread_diameter0.099 INCHES IN
screw_surface_treatmentZINC
thread_quantity_per_inch56
NSN5305-00-754-4254
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: 521397778 · 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
•
SCREW SURFACE TREATMENT: ZINC
•
FASTENER LENGTH: 0.250 INCHES NOMINAL IN
•
THREAD LENGTH: 0.219 INCHES MINIMUM IN
•
NOMINAL THREAD DIAMETER: 0.099 INCHES IN
•
HEAD STYLE: FLAT COUNTERSUNK
•
THREAD DIRECTION: RIGHT-HAND
•
SCREW MATERIAL: STEEL
•
INTERNAL DRIVE STYLE: SLOT
TECHNICAL CHARACTERISTICS
SCREW SURFACE TREATMENTZINC
FASTENER LENGTH0.250 INCHES NOMINAL IN
THREAD LENGTH0.219 INCHES MINIMUM IN
NOMINAL THREAD DIAMETER0.099 INCHES IN
HEAD STYLEFLAT COUNTERSUNK
THREAD DIRECTIONRIGHT-HAND
SCREW MATERIALSTEEL
INTERNAL DRIVE STYLESLOT
COUNTERSINK ANGLE90.0 DEGREES NOMINAL
THREAD CLASS2A A
SUBSTITUTES & CROSS-REFERENCES 1
139777Reference document
Same NSN cross-reference
Reference document — Secondary 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 521397778?
521397778 is a SCREW,MACHINE.
What parts can replace 521397778?
There is 1 known substitute for 521397778: 139777. Substitute compatibility should be verified for your specific system.
What is the NSN for 521397778?
521397778 is cataloged in the U.S. Government catalog under NSN 5305-00-754-4254. 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.