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AS21521 — BOLT,MACHINE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

AS21521: BOLT,MACHINE.

The BOLT,MACHINE is a the manufacturer industrial component. Key specifications include material: STEEL OVERALL, head_style: DOUBLE HEXAGON W/HOLE, head_height: 0.144 INCHES NOMINAL IN, thread_class: 3A A, thread_length: 0.750 INCHES MINIMUM AND 0.810 INCHES MAXIMUM IN, fastener_length: 1.312 INCHES NOMINAL IN. This part is cataloged in the U.S.

Government catalog under NSN 5306-01-166-4524, 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
AS21521
NSN: 5306-01-166-4524
FSC: 5306 — Bolts
CAGE: K7766 — BSI STANDARDS LIMITED (GBR)
SPECIFICATIONS
materialSTEEL OVERALL
head_styleDOUBLE HEXAGON W/HOLE
head_height0.144 INCHES NOMINAL IN
thread_class3A A
thread_length0.750 INCHES MINIMUM AND 0.810 INCHES MAXIMUM IN
fastener_length1.312 INCHES NOMINAL IN
thread_directionRIGHT-HAND
width_between_flats0.312 INCHES NOMINAL IN
nominal_thread_diameter0.250 INCHES IN
extended_washer_diameter0.436 INCHES NOMINAL IN
thread_quantity_per_inch28
thread_series_designatorUNIFIED NATIONAL JOINT FINE (UNJF)
NSN5306-01-166-4524
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: AS21521 · 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
•
EXTENDED WASHER THICKNESS: 0.060 INCHES NOMINAL IN
•
HEAD HEIGHT: 0.144 INCHES NOMINAL IN
•
FASTENER LENGTH: 1.312 INCHES NOMINAL IN
•
EXTENDED WASHER DIAMETER: 0.436 INCHES NOMINAL IN
•
THREAD LENGTH: 0.750 INCHES MINIMUM AND 0.810 INCHES MAXIMUM IN
•
MATERIAL DOCUMENT AND CLASSIFICATION: DTD 5026,FSCM K7766 MFR REF SINGLE MATERIAL RESPONSE OVERALL
•
NOMINAL THREAD DIAMETER: 0.250 INCHES IN
•
HEAD STYLE: DOUBLE HEXAGON W/HOLE
TECHNICAL CHARACTERISTICS
EXTENDED WASHER THICKNESS0.060 INCHES NOMINAL IN
HEAD HEIGHT0.144 INCHES NOMINAL IN
FASTENER LENGTH1.312 INCHES NOMINAL IN
EXTENDED WASHER DIAMETER0.436 INCHES NOMINAL IN
THREAD LENGTH0.750 INCHES MINIMUM AND 0.810 INCHES MAXIMUM IN
MATERIAL DOCUMENT AND CLASSIFICATIONDTD 5026,FSCM K7766 MFR REF SINGLE MATERIAL RESPONSE OVERALL
NOMINAL THREAD DIAMETER0.250 INCHES IN
HEAD STYLEDOUBLE HEXAGON W/HOLE
THREAD DIRECTIONRIGHT-HAND
WIDTH BETWEEN FLATS0.312 INCHES NOMINAL IN
OTHER ITEMS IN FSC 5306 — Bolts
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5306-00-001-1276 5306-00-001-1949 5306-00-001-1988 5306-00-001-1989 5306-00-001-1990 5306-00-001-1991 5306-00-001-1993 5306-00-001-2017
SUBSTITUTES & CROSS-REFERENCES

No substitute or cross-reference records for this part.

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 AS21521?
AS21521 is a BOLT,MACHINE.
What is the NSN for AS21521?
AS21521 is cataloged in the U.S. Government catalog under NSN 5306-01-166-4524. 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.