Pioneer Industries is a premier manufacturer and exporter of Brass Inverted Flare Long Union Nuts, engineered with an extended cylindrical barrel that damps high-frequency vibration and protects double-flared steel, copper-nickel, and copper tubing from fatigue fractures in severe automotive, truck, and hydraulic circuits.
The Brass Inverted Flare Long Union Nut from Pioneer Industries is an engineered mechanical fastening component designed to clamp double-flared tubing securely into internal inverted flare fitting ports while providing vital vibration damping. Unlike standard short inverted nuts, the long union nut features an extended cylindrical shank extending behind the external hex. This prolonged barrel supports the outer circumference of the tubing past the flare neck, effectively isolating the flared lip from severe engine vibrations and chassis bending stresses.
Manufactured strictly in compliance with SAE J512 and SAE J1231 standards, our long union nuts are precision CNC-turned from extruded high-tensile brass bar stock (BS 249 / CW614N / ASTM B16 C36000). The external Unified National Fine (UNF) straight threads are cut to Class 2A tolerances, ensuring smooth, non-binding engagement into female inverted flare ports without thread galling.
Pioneer Industries supplies Brass Inverted Flare Long Union Nuts to commercial vehicle builders, diesel engine fabricators, agricultural equipment manufacturers, and automotive aftermarket distributors across more than 85 countries worldwide. Large inventory reserves in Mumbai guarantee rapid dispatch of standard fractional sizes from 1/8" to 3/8" tube OD.
Every batch undergoes automated multi-point dimensional checking, including thread pitch diameter verification, bore concentricity inspection, and external shank runout testing. Complete material traceability is certified through EN 10204 Type 3.1 inspection documents provided with every export shipment.
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In applications subjected to continuous reciprocating vibration—such as diesel engine fuel injection feeds, tractor hydraulic connections, and commercial truck air brake lines—standard short nuts allow the tubing to flex directly at the flare neck, leading to rapid work-hardening and hairline fatigue fractures. Pioneer Industries’ Brass Inverted Flare Long Union Nut eliminates this failure mode by supporting the outer diameter of the tube over a significantly greater contact length.
The nose of the nut is machined with a precision flat clamping face that distributes axial torque evenly against the back of the double-flared copper or steel lip, driving the front face of the flare into firm, leak-tight metal-to-metal contact with the body internal seat. Rated for working pressures up to 2,800 PSI, it operates reliably across temperatures from -54°C to +121°C.
Pioneer Industries manufactures Brass Inverted Flare Long Union Nuts in tube OD sizes from 1/8" to 3/8" with male SAE UNF straight threads. Operating pressures up to 2,800 PSI (193 bar). Complies with SAE J512, SAE J1231, ASME B16.26, and ASTM B16 specifications.
Explore comprehensive engineering dimensional configurations for Fractional Inch Series, Metric Series, and Certified Material Specifications. Manufactured according to SAE J512, SAE J1231, ASME B16.26, and international standards.
| Part No. | Tube O.D. (T) | Male Thread (UNF) | Hex Size (F) | Overall Length (L) | Bore Dia (D) | Weight (approx) | Working Pressure |
|---|---|---|---|---|---|---|---|
| PI-IFLN-02 | 1/8" | 5/16-28 UNF | 5/16" | 0.62" | 0.130" | 12 g | 2,800 PSI |
| PI-IFLN-03 | 3/16" | 3/8-24 UNF | 3/8" | 0.75" | 0.193" | 18 g | 2,800 PSI |
| PI-IFLN-04 | 1/4" | 7/16-24 UNF | 7/16" | 0.84" | 0.256" | 26 g | 2,800 PSI |
| PI-IFLN-05 | 5/16" | 1/2-20 UNF | 1/2" | 0.94" | 0.318" | 36 g | 2,400 PSI |
| PI-IFLN-06 | 3/8" | 5/8-18 UNF | 5/8" | 1.06" | 0.382" | 52 g | 2,000 PSI |
| Part No. | Tube O.D. (mm) | Thread Profile (UNF) | Hex Size (mm) | Overall Length (mm) | Bore Dia (mm) | Weight (g) | Working Pressure (bar) |
|---|---|---|---|---|---|---|---|
| PI-IFLN-M04 | 4 mm | 5/16-28 UNF | 8 mm | 15.7 mm | 4.2 mm | 12 g | 193 bar |
| PI-IFLN-M05 | 5 mm | 3/8-24 UNF | 10 mm | 19.0 mm | 5.2 mm | 18 g | 193 bar |
| PI-IFLN-M06 | 6 mm | 7/16-24 UNF | 11 mm | 21.3 mm | 6.2 mm | 26 g | 193 bar |
| PI-IFLN-M08 | 8 mm | 1/2-20 UNF | 13 mm | 23.8 mm | 8.2 mm | 36 g | 165 bar |
| PI-IFLN-M10 | 10 mm | 5/8-18 UNF | 16 mm | 27.0 mm | 10.2 mm | 52 g | 138 bar |
| Component | Material Specification | Standard Specification | Chemical Composition | Mechanical Properties | Temperature Limits | Key Features |
|---|---|---|---|---|---|---|
| Precision Extruded Nut Body | Forging Brass (BS 218 / CW617N) | BS EN 12165 / ASTM B283 C37700 | Cu: 57.0–59.0%, Pb: 1.6–2.5%, Zn: Rem. | Tensile ≥ 440 MPa, 110–150 HB | -54°C to +121°C | Contoured grain flow, dense wall structure, zero porosity, high shock resistance |
| Extended Vibration Damping Shank | Free Cutting Brass (BS 249 / CW614N) | IS 319 Gr. 1 / ASTM B16 C36000 | Cu: 58.0–60.0%, Pb: 1.5–3.0%, Zn: Rem. | Tensile ≥ 400 MPa, 100–140 HB | -54°C to +121°C | Precision CNC machining, internal 42°/45° cone seat, micro-inch surface finish |
| Inverted Flare Nut | Extruded Brass / Zinc Plated Steel | SAE J512 / SAE J513 / ASTM B16 | Cu: 58.0–61.0%, Zn: Rem. | Tensile ≥ 400 MPa | -54°C to +121°C | External straight UNF male threads, hex drive, deep pilot nose for tube guidance |
| Tubing Interface | Double Flared Steel / CuNi / Copper | SAE J527 / ASTM A254 / ASTM B88 | Low Carbon Steel / CuNi 90/10 | Soft Annealed Temper | -54°C to +121°C | 100% metal-to-metal seal, zero elastomeric degradation in brake fluids & fuels |
Brass Inverted Flare Long Union Nut fittings find critical deployment across demanding automotive, mobile fluid power, and fuel delivery circuits:
Secures high-pressure fuel lines against continuous engine pulse resonance and thermal cycles.
Provides heavy-duty strain relief for copper-nickel and steel air brake tubing along chassis rails.
Protects hydraulic lines from severe vibrational fatigue adjacent to power steering pumps.
Clamps hydraulic tubing against severe mechanical shock on tractors and combines.
Secures transmission fluid lines on bulldozers and earthmovers in high-vibration applications.
Protects fuel and cooling fluid lines from structural marine hull vibrations in sea vessels.
Fastens repeated test lines subject to cyclic hydraulic hammer events.
Provides authentic SAE J512 long-nut strain relief on classic truck and performance vehicle builds.
Pioneer Industries’ Brass Inverted Flare Long Union Nut are widely used in numerous industries like:
Expert engineering insights and technical guidance regarding design specifications, pressure tolerances, internal inverted cone sealing mechanics, double flaring, and installation best practices for industrial Brass Inverted Flare Long Union Nut.
The key distinction is the overall length of the cylindrical body behind the hex drive. A Long Union Nut features an elongated smooth shank extending past the hex, providing an extended internal guide bore that supports the tubing outer diameter. This transfers the bending pivot point away from the flared lip, whereas a standard Nut is compact and intended for low-vibration or tight-clearance areas.
When metal tubing vibrates, cyclical bending stresses concentrate right at the abrupt cross-sectional transition where the tube flares outward. The extended sleeve of the Long Union Nut cradles the tube outer diameter for nearly an inch, transferring the bending pivot point to the rigid un-flared section of the tube and dramatically reducing flare neck fatigue.
In inverted flare systems (SAE J512), the fitting body houses the female cavity and internal threads. The inverted flare nut therefore has male threads on its outer diameter and a hex head on the opposite end, allowing it to screw directly into the body and press the flared tube against the internal cone.
No. Sealing is 100% mechanical between the double-flared tube face and the body internal seat. Applying thread sealant or tape to the nut threads can introduce friction errors during torquing, cross-threading, or chemical contamination into sensitive brake and fuel systems.
Our long union nuts are machined from premium BS 249 / CW614N (ASTM B16 C36000) free-cutting brass bar stock. This high-density alloy delivers exceptional tensile strength (up to 440 MPa) and resistance to stress cracking under heavy wrenching torque.
Yes. As long as the external threads are undamaged, the hex flats are not stripped, and the front clamping nose is free from gouges or distortion, the nut can be reused repeatedly across multiple tubing assemblies.
Standard tightening torque values: 3/16" tube (3/8-24 thread): 10–13 ft-lbs (14–18 N-m); 1/4" tube (7/16-24 thread): 12–15 ft-lbs (16–20 N-m); 5/16" tube (1/2-20 thread): 17–20 ft-lbs (23–27 N-m); 3/8" tube (5/8-18 thread): 25–30 ft-lbs (34–41 N-m).
Yes. Pioneer Industries Brass Inverted Flare Long Union Nuts are completely interchangeable with any standard SAE J512 or SAE J1231 female inverted flare port of matching tube and thread size.
The nut MUST be slipped over the tubing with the threaded nose pointing toward the cut end of the tube BEFORE the flare is formed. The internal bore slides smoothly over the tube OD, but once flared, the enlarged lip prevents the nut from coming off.
Every order is accompanied by EN 10204 Type 3.1 Mill Test Certificates detailing chemical analysis, tensile testing, dimensional conformance, and batch traceability from certified raw material to finished product.
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