PartsTable
Technical Data Sheet
Download PDF

HT8138-4-18T — SCREW,CLOSE TOLERANCE

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

HT8138-4-18T: SCREW,CLOSE TOLERANCE.

The SCREW,CLOSE TOLERANCE is a the manufacturer industrial component. Key specifications include material: STEEL COMP 4140 OR STEEL COMP E4340 OR STEEL COMP 6150 OR STEEL COMP 8735 OR STEEL COMP 8740 OVERALL, head_style: FLAT COUNTERSUNK, grip_length: 1.115 INCHES MINIMUM AND 1.135 INCHES MAXIMUM IN, thread_class: 3A A, grip_diameter: 0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN, head_diameter: 0.475 INCHES MINIMUM AND 0.507 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5305-00-083-3351, 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
HT8138-4-18T
NSN: 5305-00-083-3351
FSC: 5305 — Screws
CAGE: 06950 — HOWMET GLOBAL FASTENING SYSTEMS INC (USA)
SPECIFICATIONS
materialSTEEL COMP 4140 OR STEEL COMP E4340 OR STEEL COMP 6150 OR STEEL COMP 8735 OR STEEL COMP 8740 OVERALL
head_styleFLAT COUNTERSUNK
grip_length1.115 INCHES MINIMUM AND 1.135 INCHES MAXIMUM IN
thread_class3A A
grip_diameter0.2485 INCHES MINIMUM AND 0.2495 INCHES MAXIMUM IN
head_diameter0.475 INCHES MINIMUM AND 0.507 INCHES MAXIMUM IN
thread_length0.400 INCHES MINIMUM AND 0.467 INCHES MAXIMUM IN
surface_finish32.0 MICROINCHES BEARING SURFACE OF HEAD
fastener_length1.535 INCHES MINIMUM AND 1.582 INCHES MAXIMUM IN
hardness_rating36.0 ROCKWELL C MINIMUM AND 40.0 ROCKWELL C MAXIMUM OVERALL
thread_directionRIGHT-HAND
countersink_angle99.0 DEGREES MINIMUM AND 101.0 DEGREES MAXIMUM
NSN5305-00-083-3351
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: HT8138-4-18T · 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
•
SURFACE FINISH: 32.0 MICROINCHES THREADS
•
FASTENER LENGTH: 1.535 INCHES MINIMUM AND 1.582 INCHES MAXIMUM IN
•
THREAD LENGTH: 0.400 INCHES MINIMUM AND 0.467 INCHES MAXIMUM IN
•
HARDNESS RATING: 36.0 ROCKWELL C MINIMUM AND 40.0 ROCKWELL C MAXIMUM OVERALL
•
SHANK UNTHREADED HOLE DIAMETER: 0.076 INCHES MINIMUM AND 0.086 INCHES MAXIMUM FIRST HOLE IN
•
MATERIAL DOCUMENT AND CLASSIFICATION: MIL-S-5626 MIL SPEC 1ST MATERIAL RESPONSE OR MIL-S-5000 MIL SPEC 2ND MATERIAL RESPONSE OR MIL-S-8503 MIL SPEC 3RD MATERIAL RESPONSE OR MIL-S-6098 MIL SPEC 4TH MATERIAL RESPONSE OR MIL-S-6049 MIL SPEC 5TH MATERIAL RESPONSE OVERALL
•
NOMINAL THREAD DIAMETER: 0.250 INCHES IN
TECHNICAL CHARACTERISTICS
SURFACE FINISH32.0 MICROINCHES THREADS
SURFACE FINISH32.0 MICROINCHES BEARING SURFACE OF HEAD
FASTENER LENGTH1.535 INCHES MINIMUM AND 1.582 INCHES MAXIMUM IN
THREAD LENGTH0.400 INCHES MINIMUM AND 0.467 INCHES MAXIMUM IN
HARDNESS RATING36.0 ROCKWELL C MINIMUM AND 40.0 ROCKWELL C MAXIMUM OVERALL
SHANK UNTHREADED HOLE DIAMETER0.076 INCHES MINIMUM AND 0.086 INCHES MAXIMUM FIRST HOLE IN
MATERIAL DOCUMENT AND CLASSIFICATIONMIL-S-5626 MIL SPEC 1ST MATERIAL RESPONSE OR MIL-S-5000 MIL SPEC 2ND MATERIAL RESPONSE OR MIL-S-8503 MIL SPEC 3RD MATERIAL RESPONSE OR MIL-S-6098 MIL SPEC 4TH MATERIAL RESPONSE OR MIL-S-6049 MIL SPEC 5TH MATERIAL RESPONSE OVERALL
NOMINAL THREAD DIAMETER0.250 INCHES IN
HEAD STYLEFLAT COUNTERSUNK
THREAD DIRECTIONRIGHT-HAND
OTHER ITEMS IN FSC 5305 — Screws
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5305-00-001-5016 5305-00-001-9160 5305-00-001-9629 5305-00-001-9742 5305-00-001-9768 5305-00-003-4306 5305-00-003-6694 5305-00-003-6753
SUBSTITUTES & CROSS-REFERENCES 1
GB510AE4-18TSame NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Normally procured from the manufacturer (OEM)No demilitarization required
Ready to buy HT8138-4-18T?
Compare prices from verified sellers on eBay
Buy on eBay →
As an eBay Partner, PartsTable may earn a commission. Your price is not affected.
FREQUENTLY ASKED QUESTIONS
What is HT8138-4-18T?
HT8138-4-18T is a SCREW,CLOSE TOLERANCE.
What parts can replace HT8138-4-18T?
There is 1 known substitute for HT8138-4-18T: GB510AE4-18T. Substitute compatibility should be verified for your specific system.
What is the NSN for HT8138-4-18T?
HT8138-4-18T is cataloged in the U.S. Government catalog under NSN 5305-00-083-3351. This indicates validated use in U.S. government and defense supply chains.
Community Feedback
Leave a Comment
Comments are reviewed before appearing. You will receive an email to verify before your comment appears.

Request a Quote — HT8138-4-18T

✓ 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.