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Technical Data Sheet
PartsTable / COMPONENT / 21055A
21055A ✓ 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 BOLT,ECCENTRIC HEAD is a the manufacturer industrial component. Key specifications include material: STEEL COMP 3140 OVERALL, head_style: DOUBLE HEXAGON, head_height: 0.250 INCHES NOMINAL IN, thread_class: 3A A, head_diameter: 0.685 INCHES MINIMUM AND 0.688 INCHES MAXIMUM IN, fastener_length: 2.375 INCHES NOMINAL IN. This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5306-00-362-3707, 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
21055A
NSN: 5306-00-362-3707
FSC: 5306
CAGE: 1ML14 — BRINKLEY TECHNOLOGY GROUP LLC DBA HERCULES MANUFACTURING (USA)
SPECIFICATIONS
materialSTEEL COMP 3140 OVERALL
head_styleDOUBLE HEXAGON
head_height0.250 INCHES NOMINAL IN
thread_class3A A
head_diameter0.685 INCHES MINIMUM AND 0.688 INCHES MAXIMUM IN
fastener_length2.375 INCHES NOMINAL IN
hardness_rating28.0 ROCKWELL C MINIMUM AND 31.0 ROCKWELL C MAXIMUM OVERALL
thread_directionRIGHT-HAND
internal_drive_styleW/O INTERNAL DRIVE
nominal_thread_diameter0.437 INCHES IN
minimum_tensile_strength135000 POUNDS PER SQUARE INCH LBS
thread_quantity_per_inch20
NSN5306-00-362-3707
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: 21055A · 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
•
HEAD DIAMETER: 0.685 INCHES MINIMUM AND 0.688 INCHES MAXIMUM IN
•
DISTANCE FROM CENTER OF HEAD TO CENTER OF SHANK: 0.312 INCHES NOMINAL IN
•
FASTENER LENGTH: 2.375 INCHES NOMINAL IN
•
HEAD HEIGHT: 0.250 INCHES NOMINAL IN
•
INTERNAL DRIVE STYLE: W/O INTERNAL DRIVE
•
HARDNESS RATING: 28.0 ROCKWELL C MINIMUM AND 31.0 ROCKWELL C MAXIMUM OVERALL
•
DISTANCE FROM HEAD LARGEST BEARING SURFACE TO SHANK HOLE CENTER: 2.266 INCHES NOMINAL FIRST HOLE IN
•
MATERIAL DOCUMENT AND CLASSIFICATION: SAE ASSN STD SINGLE MATERIAL RESPONSE OVERALL
TECHNICAL CHARACTERISTICS (FLIS)
HEAD DIAMETER0.685 INCHES MINIMUM AND 0.688 INCHES MAXIMUM IN
DISTANCE FROM CENTER OF HEAD TO CENTER OF SHANK0.312 INCHES NOMINAL IN
FASTENER LENGTH2.375 INCHES NOMINAL IN
HEAD HEIGHT0.250 INCHES NOMINAL IN
INTERNAL DRIVE STYLEW/O INTERNAL DRIVE
HARDNESS RATING28.0 ROCKWELL C MINIMUM AND 31.0 ROCKWELL C MAXIMUM OVERALL
DISTANCE FROM HEAD LARGEST BEARING SURFACE TO SHANK HOLE CENTER2.266 INCHES NOMINAL FIRST HOLE IN
MATERIAL DOCUMENT AND CLASSIFICATIONSAE ASSN STD SINGLE MATERIAL RESPONSE OVERALL
MATERIALSTEEL COMP 3140 OVERALL
THREAD QUANTITY PER INCH20
VERIFIED SUBSTITUTES & CROSS-REFERENCES 15
121BUpgraded Successor
successor cross-reference
successor
A30512-9-5Interchangeable
interchangeable cross-reference
interchangeable
850430Interchangeable
interchangeable cross-reference
interchangeable
21055Interchangeable
interchangeable cross-reference
interchangeable
216-27212-1Interchangeable
interchangeable cross-reference
interchangeable
MIL-DTL-38449Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusCANCELLED
Availability—
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is 21055A?
21055A is a BOLT,ECCENTRIC HEAD.
What parts can replace 21055A?
There are 15 known substitutes for 21055A: 121B, A30512-9-5, 850430 and 12 more. Substitute compatibility should be verified for your specific system.
Is 21055A still available?
21055A is currently cancelled.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026