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NAS591-20H — INVERTED NUT,TUBE COUPLING

✓ Government record, cited
— · HOSE FITTING
PRODUCT OVERVIEW

NAS591-20H: INVERTED NUT,TUBE COUPLING.

The INVERTED NUT,TUBE COUPLING is a the manufacturer industrial component. Key specifications include material: ALUMINUM ALLOY, thread_size: 1-5/8-12, thread_class: 3B, overall_length: 0.750 INCHES NOMINAL IN, style_designator: INVERTED NUT, TUBE, FLARE, thread_direction: RIGHT-HAND. This part is cataloged in the U.S.

Government catalog under NSN 4730-00-142-1581, 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
NAS591-20H
NSN: 4730-00-142-1581
FSC: 4730 — Hose, Pipe, Tube, Lubrication, and Railing Fittings
CAGE: 80205 — NATIONAL AEROSPACE STANDARDS COMMITTEE AEROSPACE INDUSTRIES ASSOCIATION OF AMERICA INC NOT FOR RFQ OR SOLICITATION USE (USA)
SPECIFICATIONS
materialALUMINUM ALLOY
thread_size1-5/8-12
thread_class3B
overall_length0.750 INCHES NOMINAL IN
style_designatorINVERTED NUT, TUBE, FLARE
thread_directionRIGHT-HAND
seat_angle_in_deg33.0
surface_treatmentANODIZE
width_across_flats1.750 INCHES NOMINAL IN
casehardening_indicatorNOT CASEHARDENED
smallest_inside_diameter1.260 INCHES NOMINAL IN
screw_thread_series_designatorUN
NSN4730-00-142-1581
COMPONENT DIAGRAM
HOSE FITTING — THREAD TYPE IS CRITICAL END A: — STRAIGHT END B: — SPECIFICATIONS Thread: — Material: — Pressure: — PN: NAS591-20H · OEM ⚠ VERIFY BEFORE ORDERING NPT ≠ BSPT — tapered threads look identical but are NOT interchangeable. Wrong thread = leak. JIC (37°) ≠ AN (37°) ≠ SAE 45° — flare angles must match exactly. Measure thread pitch with gauge — visual identification is unreliable ✓ BROKER TIP Always use thread sealant (PTFE tape or pipe compound) on tapered threads (NPT/BSPT). JIC/AN flare fittings seal metal-to-metal — never use tape on flare connections PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
WIDTH ACROSS FLATS: 1.750 INCHES NOMINAL IN
•
SEAT ANGLE IN DEG: 33.0
•
TUBE OUTSIDE DIAMETER FOR WHICH DESIGNED: 1.250 INCHES NOMINAL IN
•
STYLE DESIGNATOR: INVERTED NUT, TUBE, FLARE
•
THREAD DIRECTION: RIGHT-HAND
•
CASEHARDENING INDICATOR: NOT CASEHARDENED
•
THREAD SIZE: 1-5/8-12
TECHNICAL CHARACTERISTICS
WIDTH ACROSS FLATS1.750 INCHES NOMINAL IN
SEAT ANGLE IN DEG33.0
TUBE OUTSIDE DIAMETER FOR WHICH DESIGNED1.250 INCHES NOMINAL IN
STYLE DESIGNATORINVERTED NUT, TUBE, FLARE
OVERALL LENGTH0.750 INCHES NOMINAL IN
THREAD DIRECTIONRIGHT-HAND
CASEHARDENING INDICATORNOT CASEHARDENED
THREAD SIZE1-5/8-12
SCREW THREAD SERIES DESIGNATORUN
SURFACE TREATMENTANODIZE
OTHER ITEMS IN FSC 4730 — Hose, Pipe, Tube, Lubrication, and Railing Fittings
Items in the same Federal Supply class. No interchangeability or substitution relationship is implied.
4730-00-000-1895 4730-00-000-4289 4730-00-000-4445 4730-00-000-8373 4730-00-000-8897 4730-00-001-0007 4730-00-001-0008
SUBSTITUTES & CROSS-REFERENCES 2
NAS597Reference document
Same NSN cross-reference
Reference document — Design control — primary reference
4177-20HReference document
Same NSN cross-reference
Reference document — Advisory reference — outside the item-of-supply concept
LIFECYCLE
NSN statusActive· U.S. Government catalog
No demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is NAS591-20H?
NAS591-20H is a INVERTED NUT,TUBE COUPLING.
What parts can replace NAS591-20H?
There are 2 known substitutes for NAS591-20H: NAS597, 4177-20H. Substitute compatibility should be verified for your specific system.
What is the NSN for NAS591-20H?
NAS591-20H is cataloged in the U.S. Government catalog under NSN 4730-00-142-1581. 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.