This model is discontinued
AirTAC has phased out the SI series. You can still order this code here: we ship the direct replacement SAI125AX550S, with the same bore, stroke, output force, port and mounting, so it fits the same application. The SAI replacement keeps the same ISO 15552 mounting interface, bore, stroke, output force and accessories, so it drops straight into existing fixtures. It is the current-production version of this cylinder with an upgraded piston seal.
Airtac SI125 Standard Cylinder SI125AX550S
The AirTAC SI125 Standard Cylinder SI125AX550S is a double-acting ISO 15552 (orig. ISO 6431) profile-barrel cylinder with a Ø125mm bore and 550mm stroke, G1/2 air ports and adjustable end cushioning. This model is discontinued — the direct replacement is the SAI125AX550S, which matches its ISO interface, bore, stroke, force and mounting.
- BoreØ125 mm
- Stroke550 mm
- Port sizeG1/2
- Acting typeDouble acting
- Rod threadM27×2.0
- StatusDiscontinued → SAI125AX550S
- 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 SI125 Standard Cylinder SI125AX550S
The AirTAC SI125AX550S is a discontinued double-acting ISO 15552 profile cylinder with a 125 mm bore and 550 mm stroke. It delivers 6136 N push force at 0.5 MPa. The direct replacement is the SAI125AX550S, sharing the exact bore, stroke, G1/2 port, M27x2 rod thread and ISO 15552 mounting interface for seamless fixture integration.
The SAI upgrade features a new piston seal with two Y-shaped one-way elements for low start-up pressure and long life. This SI125AX550S variant uses a SUS420J2 stainless rod (-A) and a piston magnet (-S) for CS1-B/DS1-B sensors. Note that standard cylinders drift without live air; use an external rod lock or SAIL/BSAI variant for holding.
Airtac SI125 Standard Cylinder SI125AX550S Technical Specifications
| Model | Airtac SI125 Standard Cylinder SI125AX550S |
|---|---|
| Series | SI ISO 15552 profile cylinder (discontinued) |
| Replacement | SAI125AX550S |
| Bore size | Ø125 mm |
| Stroke | 550 mm |
| Acting type | Double acting |
| Port size | G1/2 |
| Rod thread | M27×2.0 |
| Fluid | Air (filtered by 40µm element) |
|---|---|
| Operating pressure | 0.15 – 1.0 MPa |
| Proof pressure | 1.5 MPa |
| Temperature | -20 to +70 °C |
| Speed range | 30 – 500 mm/s |
| Cushion | Adjustable, 40 mm |
| Max standard stroke | Up to 1500 mm |
Specifications follow the official AirTAC SI datasheet (now discontinued). The SAI125AX550S carries the same ISO 15552 ratings. Confirm against the product label before installation. Thread options: PT / G / NPT.
Theoretical Output Force (Ø125mm)
| Pressure | Push force | Pull force |
|---|---|---|
| 0.5 MPa | 6136 N | 5734 N |
| 0.7 MPa | 8590 N | — |
| Max (@1.0 MPa) | 1251 kgf | |
The SAI125AX550S produces the same force from the same bore. Actual usable force is lower than theoretical; size with a margin.
Model Code: Airtac SI125 Standard Cylinder SI125AX550S
| SI | ISO 15552 profile-barrel cylinder (discontinued). |
|---|---|
| 125 | Bore size in mm. |
| ×550 | Stroke length in mm. |
| -S | Optional built-in magnet for sensor position sensing. |
Legacy SI-family variants: SID (double rod), SIJ (adjustable stroke) — each maps to its SAI equivalent (SID→SAID, SIJ→SAIJ). Rod material: carbon steel (blank) / SUS420J2 (A) / SUS304 (B).
Where the Airtac SI125 Standard Cylinder SI125AX550S Is Used
Heavy Press Actuation
Drives large stamping or forming presses requiring 6136 N push force at 0.5 MPa, utilizing the 550 mm stroke to cycle heavy tooling.
Bulk Material Diversion
Actuates large-scale diverters on heavy-duty conveyors, relying on the G1/2 port and adjustable 40 mm cushions for smooth end-of-stroke deceleration.
Replacing the Airtac SI125 Standard Cylinder SI125AX550S with the SAI125AX550S
To replace the SI125AX550S, order the SAI125AX550S. Verify the ISO 15552 mounting interface, 550 mm stroke, G1/2 port, and the -S magnet for legacy CS1-B/DS1-B sensors (the SAI uses current AirTAC switches). The -A rod denotes SUS420J2 stainless steel. For sizing alternatives, a 100 mm bore yields 3927 N push at 0.5 MPa, while a 160 mm bore yields 10053 N. At 0.7 MPa this 125 mm bore outputs 8590 N. Because the stroke is 550 mm, add external guides to prevent rod bending under side loads. A plain cylinder does not hold load without air; for secure holding, select the SAIL or BSAI lock variant, or use a pilot check valve.
Replacement checklist
- ✓ Same ISO 15552 interface → SAI125AX550S
- ✓ Same bore / stroke / force
- ✓ Port/thread type (PT/G/NPT)
- ✓ Magnet (-S) for sensors?
- ✓ Mounting reused (FA/FB/CA/CB/CR/LB/TC)
Airtac SI125 Standard Cylinder SI125AX550S FAQ
Yes, the SI125AX550S is discontinued. The direct replacement is the SAI125AX550S. It is dimensionally interchangeable per ISO 15552, retaining the same 125 mm bore, 550 mm stroke, output force, G1/2 port and mounting interface.
This 125 mm bore cylinder features a G1/2 air port. It delivers 6136 N push and 5734 N pull at 0.5 MPa, 8590 N push at 0.7 MPa, 11045 N push at 0.9 MPa, and a theoretical max of 1251 kgf at 1.0 MPa. Operating speed is 30-500 mm/s.
Related AirTAC SAI Cylinders
Request a Quote for the SAI125AX550S
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