Pioneer Industries is a globally renowned manufacturer and exporter of Brass Inverted Flare Nuts, engineered to provide high-torque mechanical clamping for double-flared copper, bundy steel, and copper-nickel tubing in automotive brake, fuel, and transmission fluid circuits.
The Brass Inverted Flare Nut manufactured by Pioneer Industries is the indispensable mechanical fastening component of any SAE J512 inverted flared tubing assembly. Featuring precision-cut external Unified National Fine (UNF) straight threads and an integrated hexagonal driving head, this male-threaded nut slides over the tubing prior to flaring and threads directly into the female inverted flare port of fitting bodies, master cylinders, or fuel valves, exerting uniform axial clamping force against the back of the flared tube lip.
Engineered to SAE J512 and SAE J1231 automotive standards, our brass inverted flare nuts are precision CNC-turned from high-tensile extruded brass bar stock (BS 249 / CW614N / ASTM B16 C36000). The high-density metallurgy prevents thread stripping, flaring bell-mouthing, and stress-cracking under heavy wrenching torque and cyclic thermal conditions.
Pioneer Industries exports millions of Brass Inverted Flare Nuts annually to automotive OEMs, commercial vehicle manufacturers, brake line fabricators, and plumbing 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 is manufactured under an ISO 9001:2015 certified quality system. Thread pitch tolerances, bore concentricity, and pilot nose squareness are verified using computerized optical measurement systems. Dispatched lots are certified with EN 10204 Type 3.1 material test certificates.
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The reliability of an automotive hydraulic brake joint depends directly on the accuracy of the inverted flare nut. Poorly machined nuts with eccentric bores, rough nose faces, or undersized hex flats lead to uneven flare compression, galling, and catastrophic fluid leaks. Pioneer Industries’ Brass Inverted Flare Nut is engineered with a micro-smooth pilot nose that supports the back of the double-flared tube uniformly around its entire 360-degree perimeter.
Our nuts are manufactured with precision Class 2A threads that engage smoothly by hand, eliminating cross-threading risks during awkward under-chassis installations. When tightened to specified torque, the nut creates an impenetrable metal-to-metal wedge seal between the tube flare and the internal seat, operating reliably up to 2,800 PSI across temperatures from -54°C to +121°C.
Pioneer Industries manufactures Brass Inverted Flare Nuts in standard fractional sizes from 1/8" to 3/8" tube OD with male SAE UNF straight threads. Operating pressures up to 2,800 PSI (193 bar). Conforms to SAE J512, SAE J1231, ASME B16.26, and ASTM B16 standards.
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-IFN-02 | 1/8" | 5/16-28 UNF | 5/16" | 0.44" | 0.130" | 8 g | 2,800 PSI |
| PI-IFN-03 | 3/16" | 3/8-24 UNF | 3/8" | 0.56" | 0.193" | 12 g | 2,800 PSI |
| PI-IFN-04 | 1/4" | 7/16-24 UNF | 7/16" | 0.59" | 0.256" | 18 g | 2,800 PSI |
| PI-IFN-05 | 5/16" | 1/2-20 UNF | 1/2" | 0.62" | 0.318" | 24 g | 2,400 PSI |
| PI-IFN-06 | 3/8" | 5/8-18 UNF | 5/8" | 0.72" | 0.382" | 38 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-IFN-M04 | 4 mm | 5/16-28 UNF | 8 mm | 11.2 mm | 4.2 mm | 8 g | 193 bar |
| PI-IFN-M05 | 5 mm | 3/8-24 UNF | 10 mm | 14.2 mm | 5.2 mm | 12 g | 193 bar |
| PI-IFN-M06 | 6 mm | 7/16-24 UNF | 11 mm | 15.0 mm | 6.2 mm | 18 g | 193 bar |
| PI-IFN-M08 | 8 mm | 1/2-20 UNF | 13 mm | 15.7 mm | 8.2 mm | 24 g | 165 bar |
| PI-IFN-M10 | 10 mm | 5/8-18 UNF | 16 mm | 18.3 mm | 10.2 mm | 38 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 |
| Flat Precision Clamping Nose | 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 Nut fittings find critical deployment across demanding automotive, mobile fluid power, and fuel delivery circuits:
Secures rigid brake lines into master cylinders, ABS modulators, and proportioning valves.
Fastens steel and copper-nickel fuel delivery lines into fuel filter and carburetor inlets.
Clamps fluid lines against power steering pump pressure ports.
Secures transmission oil lines entering radiator bottom tanks.
Fastens copper-nickel tubing inside commercial truck chassis air control valves.
Secures pilot hydraulic lines on excavators, tractors, and agricultural machinery.
Fastens high-density metal lines inside automated control skids.
Essential replacement fastener for brake line replacement and custom vehicle restorations.
Pioneer Industries’ Brass Inverted Flare 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 Nut.
A Brass Inverted Flare Nut is a male-threaded fastener that has external straight UNF threads and a hexagonal driving head. It slides over tubing prior to flaring and threads directly into a female inverted flare cavity. In contrast, a standard flare nut has internal female threads that screw over an externally threaded male fitting body.
No. The inner bore of the inverted flare nut is sized just slightly larger than the tube outer diameter, and smaller than the flared lip. Therefore, the nut MUST be slipped onto the tubing with the threaded nose facing toward the cut end before flaring.
These nuts utilize straight Unified National Fine (UNF) Class 2A external threads per SAE J512 standards (e.g. 3/8-24 for 3/16" tube, 7/16-24 for 1/4" tube, and 1/2-20 for 5/16" tube). These straight threads generate axial clamping force and do not seal along thread flanks.
No. Applying thread sealant or PTFE tape to inverted flare nut threads is unnecessary and strongly discouraged. Sealing is 100% metal-to-metal between the double-flared tube lip and the internal brass seat. Sealant on threads can cause friction errors during torquing or contaminate brake fluids and fuels.
Recommended 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).
Over-tightening can crush or crack the copper or steel double flare, strip the female body threads, or cause flare lip distortion that results in fluid weeping under pressure. Always use a calibrated torque wrench or follow standard one-flat (60°) tightening past finger-tight.
Our inverted flare nuts are machined from high-tensile BS 249 / CW614N (ASTM B16 C36000) extruded brass bar, providing tensile strength exceeding 400 MPa and superior resistance to stress cracking.
Yes. Pioneer Industries brass inverted flare nuts are fully compatible with low-carbon bundy steel tubing, Copper-Nickel (CuNi 90/10) tubing, and seamless copper lines, offering excellent galvanic compatibility and zero rust seizing.
Yes. An inverted flare nut can be reused multiple times provided its threads are clean and undamaged, the hex flats are not stripped, and the front clamping nose is smooth and free from burrs or deep gouges.
Pioneer Industries supplies EN 10204 Type 3.1 Mill Test Certificates verifying raw material chemical composition, mechanical properties, and dimensional conformity with each shipment.
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