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Technical Data Sheet
PartsTable / COMPONENT / 16991-4C20
16991-4C20 ✓ Verified by PartsTable
— · BOLT SCREW
WHAT YOU NEED TO KNOW
Grade/class stamped on head determines strength Metric and imperial threads look similar — measure pitch
Verify thread pitch — metric != imperial
PRODUCT OVERVIEW

The SCREW,MACHINE is a the manufacturer industrial component. Key specifications include head_style: FLAT COUNTERSUNK, thread_class: 3A A, head_diameter: 0.480 INCHES MINIMUM AND 0.531 INCHES MAXIMUM IN, screw_material: STEEL CORROSION RESISTING, fastener_length: 1.250 INCHES NOMINAL IN, thread_direction: RIGHT-HAND. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5305-01-481-3940, 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
16991-4C20
NSN: 5305-01-481-3940
FSC: 5305
CAGE: 56878 — SPS TECHNOLOGIES, LLC DBA PB FASTENERS (USA)
SPECIFICATIONS
head_styleFLAT COUNTERSUNK
thread_class3A A
head_diameter0.480 INCHES MINIMUM AND 0.531 INCHES MAXIMUM IN
screw_materialSTEEL CORROSION RESISTING
fastener_length1.250 INCHES NOMINAL IN
thread_directionRIGHT-HAND
countersink_angle80.0 DEGREES MINIMUM AND 82.0 DEGREES MAXIMUM
nominal_thread_diameter0.250 INCHES IN
thread_quantity_per_inch20
thread_series_designatorUNRC
NSN5305-01-481-3940
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: 16991-4C20 · 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
•
THREAD DIRECTION: RIGHT-HAND
•
COUNTERSINK ANGLE: 80.0 DEGREES MINIMUM AND 82.0 DEGREES MAXIMUM
•
HEAD DIAMETER: 0.480 INCHES MINIMUM AND 0.531 INCHES MAXIMUM IN
•
SCREW MATERIAL: STEEL CORROSION RESISTING
•
THREAD QUANTITY PER INCH: 20
•
HEAD STYLE: FLAT COUNTERSUNK
•
THREAD SERIES DESIGNATOR: UNRC
•
NOMINAL THREAD DIAMETER: 0.250 INCHES IN
TECHNICAL CHARACTERISTICS (FLIS)
THREAD DIRECTIONRIGHT-HAND
COUNTERSINK ANGLE80.0 DEGREES MINIMUM AND 82.0 DEGREES MAXIMUM
HEAD DIAMETER0.480 INCHES MINIMUM AND 0.531 INCHES MAXIMUM IN
SCREW MATERIALSTEEL CORROSION RESISTING
THREAD QUANTITY PER INCH20
HEAD STYLEFLAT COUNTERSUNK
THREAD SERIES DESIGNATORUNRC
NOMINAL THREAD DIAMETER0.250 INCHES IN
THREAD CLASS3A A
FASTENER LENGTH1.250 INCHES NOMINAL IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 6
804792Interchangeable
interchangeable cross-reference
interchangeable
31094Interchangeable
interchangeable cross-reference
interchangeable
YTA170523Interchangeable
interchangeable cross-reference
interchangeable
CX187073Interchangeable
interchangeable cross-reference
interchangeable
1134090Interchangeable
interchangeable cross-reference
interchangeable
310.94Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is 16991-4C20?
16991-4C20 is a SCREW,MACHINE.
What parts can replace 16991-4C20?
There are 6 known substitutes for 16991-4C20: 804792, 31094, YTA170523 and 3 more. Substitute compatibility should be verified for your specific system.
What is the NSN for 16991-4C20?
16991-4C20 is cataloged in the Federal Logistics Information System (FLIS) under NSN 5305-01-481-3940. This indicates validated use in U.S. government and defense supply chains.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026