Airtac PG Reducing Union PG8-4D
The AirTAC Airtac PG Reducing Union PG8-4D is a genuine different diameter straight for push-in tube connection, rated 0 - 1.0 MPa (0 - 10 kgf/cm2) with a 1.5 MPa proof pressure.
- TypeDifferent diameter straight
- SeriesPG
- Working pressure0 - 1.0 MPa (0 - 10 kgf/cm2)
- Proof pressure1.5 MPa
- Temperature-20 to +70 °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 PG Reducing Union PG8-4D
The PG8-4D is an AirTAC PG series different diameter straight union - a tube-to-tube reducer with no threaded port at all. One end accepts Dia 8 mm tubing, the other Dia 4 mm, and the two legs are in line, so the part sits invisibly inside a straight tube run while stepping the bore down. Both sides are one-touch: push the soft nylon or polyurethane tube in until it bottoms, and the internal chuck grips the OD; press the POM release ring toward the body and the tube slides free.
This is the resin one-touch profile, not the metal BP line: working pressure 0-1.0 MPa (0-10 kgf/cm2), vacuum to -750 mmHg (10 Torr), proof pressure 1.5 MPa, and a -20 to +70 C temperature window. The D suffix gives the whole body black colouring on PG, not just the button. Inside are a POM release button and chuck, an aluminium-alloy guide, a stainless spring gasket and an NBR O-ring. Note that the 4 mm leg halves the bore of the 8 mm leg, so whatever you feed through this union is limited by the 4 mm side.
Airtac PG Reducing Union PG8-4D Technical Specifications
| Model | Airtac PG Reducing Union PG8-4D |
|---|---|
| Type | Different diameter straight |
| Series | PG |
| Connection | Push-in one-touch |
| Working pressure | 0 - 1.0 MPa (0 - 10 kgf/cm2) |
|---|---|
| Negative pressure | -750 mmHg (10 Torr) |
| Proof pressure | 1.5 MPa |
| Temperature | -20 to +70 °C |
| Applicable tubing | Soft nylon or polyurethane tube |
| Thread standard | PT (Rc tapered) unless the code says otherwise |
POM release button and chuck, aluminium-alloy guide, stainless spring gasket, NBR O-ring; body brass or PBT depending on the part. AirTAC publishes flow as a characteristic curve rather than a single figure, so no L/min value is listed.
Model Code: Airtac PG Reducing Union PG8-4D
| PG | Different diameter straight. |
|---|---|
| 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 PG Reducing Union PG8-4D Is Used
Packaging machine air jet drop
A packaging machine carries 8 mm trunk lines from the valve manifold, but the air-blast nozzles that clear film from the sealing bar are plumbed in 4 mm tube. PG8-4D makes that step in-line inside the guard with no threaded adapter.
Vacuum pad feed on an electronics head
A PCB pick-and-place head draws vacuum through slim 4 mm lines, while the ejector supply on the gantry is run in 8 mm. This union steps the vacuum generator's supply down at the head end, and the one-touch release lets the head be serviced quickly.
Pilot line tap inside a control cabinet
A machine builder wants a 4 mm pilot signal line tapped off an 8 mm actuator supply run inside the electrical cabinet's pneumatic section. The black PG8-4D body blends with dark wiring ducting and needs zero tools to install.
Is the Airtac PG Reducing Union PG8-4D the Right Part?
Step carefully on this ladder. If a 8-to-4 drop is too aggressive, the same family offers PG8-6, which steps 8 mm down to 6 mm and keeps much more of the bore; if you are already on 6 mm tube, PG6-4 makes the same 4 mm landing without starting from 8 mm. Every step changes the choke point of the circuit - with PG8-4D the 4 mm leg is the narrowest passage, so size downstream actuators around that bore, not the 8 mm supply.
Tube OD must match exactly on both legs. A nominal 1/4 in tube measures about 6.35 mm and will neither seal nor release correctly in a Dia 6 or Dia 4 port, so resist any temptation to make it fit. If you actually need this reduction to pass through a cabinet wall or panel, use the PM bulkhead union family instead of forcing a straight union into a hole; PG8-4D is for in-line runs inside a machine frame or on a manifold face.
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 -20 to +70 °C
Airtac PG Reducing Union PG8-4D FAQ
PG8-4D is a resin one-touch different diameter straight union joining Dia 8 mm tube to Dia 4 mm tube. Working pressure is 0-1.0 MPa (0-10 kgf/cm2), it holds vacuum down to -750 mmHg (10 Torr), proof pressure is 1.5 MPa, and the working temperature range is -20 to +70 C. Use only soft nylon or polyurethane tubing; AirTAC publishes capacity for this series as a characteristic curve, not a single flow number, and the 4 mm leg is the bore limit.
No. One-touch chucks and O-rings are machined for one exact tube OD per port, so the Dia 8 leg takes only 8 mm tube and the Dia 4 leg only 4 mm tube. A nominal 1/4 in tube measures about 6.35 mm, which will not seal in either port. If your existing run is in inches, stay within the inch-sized fitting range rather than adapting this metric union.
Authorized Export Seller
Genuine AirTAC parts produced by AirTAC factory.
1-Year Warranty
Covers non-human-caused product damage.
Fast Dispatch
Standard parts are processed and dispatched in 3-5 business days.
Fast Reply
Most inquiries answered within 7-8 hours.
Related AirTAC One-Touch Fittings
Request a Quote for Airtac PG Reducing Union PG8-4D
Send us the quantity and destination. We confirm price, stock and lead time — usually within 7-8 hours.