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78991 — SCREW,CAP,HEXAGON HEAD

✓ Government record, cited
— · BOLT SCREW
PRODUCT OVERVIEW

78991: SCREW,CAP,HEXAGON HEAD.

The SCREW,CAP,HEXAGON HEAD is a the manufacturer industrial component. Key specifications include material: STEEL OVERALL, head_style: HEXAGON, head_height: 0.105 INCHES MINIMUM AND 0.120 INCHES MAXIMUM IN, thread_class: 2A A, thread_length: 0.750 INCHES MINIMUM IN, fastener_length: 5.320 INCHES MINIMUM AND 5.440 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5305-01-077-9659, 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
78991
NSN: 5305-01-077-9659
FSC: 5305 — Screws
CAGE: 24975 — PRESTOLITE ELECTRIC INC (USA)
SPECIFICATIONS
materialSTEEL OVERALL
head_styleHEXAGON
head_height0.105 INCHES MINIMUM AND 0.120 INCHES MAXIMUM IN
thread_class2A A
thread_length0.750 INCHES MINIMUM IN
fastener_length5.320 INCHES MINIMUM AND 5.440 INCHES MAXIMUM IN
hardness_rating25.0 ROCKWELL C MINIMUM AND 34.0 ROCKWELL C MAXIMUM OVERALL
thread_directionRIGHT-HAND
surface_treatmentCADMIUM OVERALL
width_between_flats0.305 INCHES MINIMUM AND 0.312 INCHES MAXIMUM IN
nominal_thread_diameter0.190 INCHES IN
minimum_tensile_strength120000 POUNDS PER SQUARE INCH LBS
NSN5305-01-077-9659
COMPONENT DIAGRAM
BOLT / SCREW — THREAD VERIFICATION REQUIRED Hex HEAD LENGTH: — THREAD: — × — MATERIAL: — PN: 78991 · 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 HEIGHT: 0.105 INCHES MINIMUM AND 0.120 INCHES MAXIMUM IN
•
FASTENER LENGTH: 5.320 INCHES MINIMUM AND 5.440 INCHES MAXIMUM IN
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: QQ-P-416,TY 1,CL 3 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
•
THREAD LENGTH: 0.750 INCHES MINIMUM IN
•
HARDNESS RATING: 25.0 ROCKWELL C MINIMUM AND 34.0 ROCKWELL C MAXIMUM OVERALL
•
NOMINAL THREAD DIAMETER: 0.190 INCHES IN
•
HEAD STYLE: HEXAGON
•
THREAD DIRECTION: RIGHT-HAND
TECHNICAL CHARACTERISTICS
HEAD HEIGHT0.105 INCHES MINIMUM AND 0.120 INCHES MAXIMUM IN
FASTENER LENGTH5.320 INCHES MINIMUM AND 5.440 INCHES MAXIMUM IN
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONQQ-P-416,TY 1,CL 3 FED SPEC SINGLE TREATMENT RESPONSE OVERALL
THREAD LENGTH0.750 INCHES MINIMUM IN
HARDNESS RATING25.0 ROCKWELL C MINIMUM AND 34.0 ROCKWELL C MAXIMUM OVERALL
NOMINAL THREAD DIAMETER0.190 INCHES IN
HEAD STYLEHEXAGON
THREAD DIRECTIONRIGHT-HAND
WIDTH BETWEEN FLATS0.305 INCHES MINIMUM AND 0.312 INCHES MAXIMUM IN
SURFACE TREATMENTCADMIUM OVERALL
OTHER ITEMS IN FSC 5305 — Screws
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
5305-00-000-0094 5305-00-000-1397 5305-00-000-2625 5305-00-000-3669 5305-00-000-3830 5305-00-000-3831
SUBSTITUTES & CROSS-REFERENCES 1
A104-078991Reference document
Same NSN cross-reference
Reference document — Secondary reference
LIFECYCLE
NSN statusActive· U.S. Government catalog
Acquisition advice: Normally procured from the manufacturer (OEM)No demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is 78991?
78991 is a SCREW,CAP,HEXAGON HEAD.
What parts can replace 78991?
There is 1 known substitute for 78991: A104-078991. Substitute compatibility should be verified for your specific system.
What is the NSN for 78991?
78991 is cataloged in the U.S. Government catalog under NSN 5305-01-077-9659. 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.