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ST7M257-550H312 — COUPLING,TUBE

✓ Government record, cited
— · HOSE FITTING
PRODUCT OVERVIEW

ST7M257-550H312: COUPLING,TUBE.

The COUPLING,TUBE is a the manufacturer industrial component. Key specifications include material: STEEL CORROSION RESISTING OVERALL, connection_type: UNTHREADED INTERNAL TUBE ALL ENDS, connection_style: PLAIN (TUBE) ALL ENDS, style_designator: PLAIN W/TAPERED ENDS, surface_treatment: PASSIVATE OVERALL, operating_pressure: 45.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS. This part is cataloged in the U.S.

Government catalog under NSN 4730-01-070-3393, 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
ST7M257-550H312
NSN: 4730-01-070-3393
FSC: 4730 — Hose, Pipe, Tube, Lubrication, and Railing Fittings
CAGE: 76301 — THE BOEING COMPANY DIV DEFENSE (USA)
SPECIFICATIONS
materialSTEEL CORROSION RESISTING OVERALL
connection_typeUNTHREADED INTERNAL TUBE ALL ENDS
connection_stylePLAIN (TUBE) ALL ENDS
style_designatorPLAIN W/TAPERED ENDS
surface_treatmentPASSIVATE OVERALL
operating_pressure45.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS
maximum_operating_temp-65.0 FAHRENHEIT FIRST RESPONSE DEGF
nominal_overall_length3.120 INCHES IN
media_for_which_designedAERONAUTICAL FLUID SINGLE RESPONSE
material_document_and_classificationMIL-S-6721,TYPE 321 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-T-8808 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
nominal_outside_diameter_tube_accommodated5.590 INCHES ALL ENDS IN
surface_treatment_document_and_classificationMIL-S-5002 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
NSN4730-01-070-3393
COMPONENT DIAGRAM
HOSE FITTING — THREAD TYPE IS CRITICAL END A: — STRAIGHT END B: — SPECIFICATIONS Thread: — Material: — Pressure: — PN: ST7M257-550H312 · 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
•
SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: MIL-S-5002 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
•
CONNECTION STYLE: PLAIN (TUBE) ALL ENDS
•
TUBING WALL NOMINAL THICKNESS FOR WHICH DESIGNED: 0.035 INCHES ALL ENDS IN
•
NOMINAL OVERALL LENGTH: 3.120 INCHES IN
•
CONNECTION TYPE: UNTHREADED INTERNAL TUBE ALL ENDS
•
STYLE DESIGNATOR: PLAIN W/TAPERED ENDS
•
MATERIAL DOCUMENT AND CLASSIFICATION: MIL-S-6721,TYPE 321 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-T-8808 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
•
NOMINAL OUTSIDE DIAMETER TUBE ACCOMMODATED: 5.590 INCHES ALL ENDS IN
TECHNICAL CHARACTERISTICS
SURFACE TREATMENT DOCUMENT AND CLASSIFICATIONMIL-S-5002 MIL SPEC SINGLE TREATMENT RESPONSE OVERALL
CONNECTION STYLEPLAIN (TUBE) ALL ENDS
TUBING WALL NOMINAL THICKNESS FOR WHICH DESIGNED0.035 INCHES ALL ENDS IN
NOMINAL OVERALL LENGTH3.120 INCHES IN
CONNECTION TYPEUNTHREADED INTERNAL TUBE ALL ENDS
STYLE DESIGNATORPLAIN W/TAPERED ENDS
MATERIAL DOCUMENT AND CLASSIFICATIONMIL-S-6721,TYPE 321 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-T-8808 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
NOMINAL OUTSIDE DIAMETER TUBE ACCOMMODATED5.590 INCHES ALL ENDS IN
OPERATING PRESSURE45.0 POUNDS PER SQUARE INCH (PSI) MAXIMUM SINGLE RESPONSE LBS
MAXIMUM OPERATING TEMP-65.0 FAHRENHEIT FIRST RESPONSE DEGF
SUBSTITUTES & CROSS-REFERENCES 2
10A347-550-312Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
ST7M257Reference document
Same NSN cross-reference
Reference document — Drawing number reference only
LIFECYCLE
NSN statusActive· U.S. Government catalog
No demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is ST7M257-550H312?
ST7M257-550H312 is a COUPLING,TUBE.
What parts can replace ST7M257-550H312?
There are 2 known substitutes for ST7M257-550H312: 10A347-550-312, ST7M257. Substitute compatibility should be verified for your specific system.
What is the NSN for ST7M257-550H312?
ST7M257-550H312 is cataloged in the U.S. Government catalog under NSN 4730-01-070-3393. 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.