Airtac BU Double Female Thread Straight Connector BU0404
The AirTAC Airtac BU Double Female Thread Straight Connector BU0404 is a genuine double female connector rated to 3.0 MPa proof pressure and 0 to +150 °C, for joining threaded pipe runs.
- TypeDouble female connector
- SeriesBU
- Working pressure0 - 1.0 MPa (0 - 10 kgf/cm2)
- Proof pressure3.0 MPa
- Temperature0 to +150 °C
- No minimum order. A single piece can be ordered.
- Ready in 3–5 business days. That is the time we take to process the order and hand it to the carrier. Transit time after that depends on the destination.
About the Airtac BU Double Female Thread Straight Connector BU0404
The BU0404 is a straight double female connector: both ends carry internal 1/2in PT thread, so it joins two male-threaded stubs face to face as one continuous 1/2in line. Unlike the BB male connector, nothing here protrudes into a component port - the part sits inside the pipework between two male ends.
It belongs to AirTAC's nickel-plated metal joint family, and the numbers set it apart from one-touch resin fittings: 0-1.0 MPa working pressure, 3.0 MPa proof pressure and a 0 to 150 C temperature band with -750 mmHg vacuum capability. That is why this style is specified near dryers, ovens and hot process equipment, where a push-in resin body would soften. Metal fittings also suit hot environments, but always confirm the tube's own temperature rating first - the tube is normally the limit, not the joint.
Airtac BU Double Female Thread Straight Connector BU0404 Technical Specifications
| Model | Airtac BU Double Female Thread Straight Connector BU0404 |
|---|---|
| Type | Double female connector |
| Series | BU |
| Connection | Threaded both ends |
| Working pressure | 0 - 1.0 MPa (0 - 10 kgf/cm2) |
|---|---|
| Negative pressure | -750 mmHg (10 Torr) |
| Proof pressure | 3.0 MPa |
| Temperature | 0 to +150 °C |
| Thread standard | PT (Rc tapered) unless the code says otherwise |
Nickel-plated metal body. AirTAC does not publish a per-part material breakdown for this family. This family is rated to 150 °C, but the TUBE is usually the limit - confirm your tubing's temperature rating before running it hot. AirTAC publishes flow as a characteristic curve rather than a single figure, so no L/min value is listed.
Model Code: Airtac BU Double Female Thread Straight Connector BU0404
| BU | Double female connector. |
|---|---|
| 4 / 6 / 8 / 10 / 12 | Tube outside diameter in mm (3.2 mm exists on the mini series). |
| M5 / 01 / 02 / 03 / 04 | Thread: M5x0.8, 1/8", 1/4", 3/8", 1/2" (M3 on the mini series). |
| D | Black. Blank = grey. |
Fitting & Sealing Notes
- check Cut the tube square and clean before pushing it home, or the seal will leak.
- check Push until it stops, then pull back to check the chuck has gripped.
- check To release, press the collet ring fully in and pull the tube out.
- check Threaded parts arrive with sealant on the thread; M5 sizes use a sealing gasket.
- check Match the tube OD exactly - a 6 mm fitting will not hold 1/4" tube.
Where the Airtac BU Double Female Thread Straight Connector BU0404 Is Used
Heat-shrink tunnel air circuits
Packaging lines with shrink tunnels run hot air well past 70 C around the film zone. A 1/2in BU0404 unions the male-threaded air spurs feeding the tunnel's blower and nozzle manifold without a resin joint in the hot path.
Injection mould tooling airlines
Ejector-assist and core-pull air circuits on plastic injection moulds sit close to the hot half of the tool. Joining the 1/2in PT stubs from the mould plate and the manifold with a BU0404 keeps a metal joint where ambient heat would creep a plastic body.
Textile stenter and laundry lines
Stenter frames and commercial laundry equipment pipe compressed air alongside heated drying sections. A double female union lets maintenance crews break the line at two male threaded points for service, then remake it with the same BU0404.
Is the Airtac BU Double Female Thread Straight Connector BU0404 the Right Part?
BU0404 sits at the top of the BU ladder - BU0404 is the largest double female connector in the range, so there is no step up. The only neighbouring same-size unit below it is BU0303 (3/8in PT both ends); dropping to BU0303 buys a smaller, cheaper union where the circuit is 3/8in, but halves the bore feeding the line. If your circuit is genuinely 1/2in, this is the part.
If one end must be male instead of female, the like-for-like 1/2in part is BB0404 (male 1/2in to male 1/2in). For a reducing joint that mixes female 3/8in with male 1/2in, BD0304 does it in one body rather than a BU0404 plus a reducing bushing. BU units exist only in matched same-size pairs - there is no reducing double female connector in this series, so never specify one.
Quick checklist
- ✓ Tube outside diameter matches exactly
- ✓ Thread size and standard match the port
- ✓ Working pressure within 0 - 1.0 MPa (0 - 10 kgf/cm2)
- ✓ Temperature within 0 to +150 °C
Airtac BU Double Female Thread Straight Connector BU0404 FAQ
Working pressure 0-1.0 MPa (0-10 kgf/cm2), negative pressure to -750 mmHg (10 Torr), proof pressure 3.0 MPa, and a temperature range of 0 to 150 C. This SKU is a double female connector with internal 1/2in PT thread on both ends and a nickel-plated body. Proof pressure is twice the 1.5 MPa figure quoted for one-touch resin fittings - do not mix the two ratings.
Both ends are female PT (taper) thread, so seal each male thread with PTFE tape or an approved thread sealant before threading the BU0404 on - PT threads seal through the taper, not a face seal. Support the connector with a spanner on its flats while tightening either male end, and do not over-torque the cast body. Because the same 1/2in internal thread runs through the part, flow capacity is set by the 1/2in bore of the line itself; see the published characteristic curve rather than a quoted flow value.
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