PartsTable
Technical Data Sheet
PartsTable / COMPONENT / FF-S-21
FF-S-21 ✓ 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 SETSCREW is a the manufacturer industrial component. Key specifications include head_style: SQUARE, head_height: 0.178 INCHES MINIMUM AND 0.196 INCHES MAXIMUM IN, point_style: CUP, thread_class: 3A A, fastener_length: 1.438 INCHES MINIMUM AND 1.500 INCHES MAXIMUM IN, hardness_rating: 45.0 ROCKWELL C MINIMUM AND 53.0 ROCKWELL C MAXIMUM OVERALL. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5305-00-249-0591, 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
FF-S-21
NSN: 5305-00-249-0591
FSC: 5305
CAGE: 81348 — FEDERAL SPECIFICATIONS PROMULGATED BY GENERAL SERVICES ADMINISTRATION WASHINGTON DC (USA)
SPECIFICATIONS
head_styleSQUARE
head_height0.178 INCHES MINIMUM AND 0.196 INCHES MAXIMUM IN
point_styleCUP
thread_class3A A
fastener_length1.438 INCHES MINIMUM AND 1.500 INCHES MAXIMUM IN
hardness_rating45.0 ROCKWELL C MINIMUM AND 53.0 ROCKWELL C MAXIMUM OVERALL
thread_directionRIGHT-HAND
width_between_flats0.241 INCHES MINIMUM AND 0.250 INCHES MAXIMUM IN
internal_drive_styleW/O INTERNAL DRIVE
nominal_thread_diameter0.250 INCHES IN
thread_quantity_per_inch20
thread_series_designatorUNIFIED NATIONAL COARSE (UNC)
NSN5305-00-249-0591
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: FF-S-21 · 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 SERIES DESIGNATOR: UNIFIED NATIONAL COARSE (UNC)
•
HARDNESS RATING: 45.0 ROCKWELL C MINIMUM AND 53.0 ROCKWELL C MAXIMUM OVERALL
•
NONDEFINITIVE SPEC/STD DATA: A TYPE
•
FASTENER LENGTH: 1.438 INCHES MINIMUM AND 1.500 INCHES MAXIMUM IN
•
THREAD CLASS: 3A A
•
WIDTH BETWEEN FLATS: 0.241 INCHES MINIMUM AND 0.250 INCHES MAXIMUM IN
•
HEAD STYLE: SQUARE
•
THREAD QUANTITY PER INCH: 20
TECHNICAL CHARACTERISTICS (FLIS)
THREAD SERIES DESIGNATORUNIFIED NATIONAL COARSE (UNC)
HARDNESS RATING45.0 ROCKWELL C MINIMUM AND 53.0 ROCKWELL C MAXIMUM OVERALL
NONDEFINITIVE SPEC/STD DATAA TYPE
FASTENER LENGTH1.438 INCHES MINIMUM AND 1.500 INCHES MAXIMUM IN
THREAD CLASS3A A
WIDTH BETWEEN FLATS0.241 INCHES MINIMUM AND 0.250 INCHES MAXIMUM IN
HEAD STYLESQUARE
THREAD QUANTITY PER INCH20
POINT STYLECUP
HEAD HEIGHT0.178 INCHES MINIMUM AND 0.196 INCHES MAXIMUM IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 6
P1310-33Interchangeable
interchangeable cross-reference
interchangeable
P1463PCP1310-33Interchangeable
interchangeable cross-reference
interchangeable
P1310APCP1310-33Interchangeable
interchangeable cross-reference
interchangeable
MILB933TYPEAInterchangeable
interchangeable cross-reference
interchangeable
E87886-2Interchangeable
interchangeable cross-reference
interchangeable
FF-S-210Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is FF-S-21?
FF-S-21 is a SETSCREW.
What parts can replace FF-S-21?
There are 6 known substitutes for FF-S-21: P1310-33, P1463PCP1310-33, P1310APCP1310-33 and 3 more. Substitute compatibility should be verified for your specific system.
What is the NSN for FF-S-21?
FF-S-21 is cataloged in the Federal Logistics Information System (FLIS) under NSN 5305-00-249-0591. 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