Pneumatic Self-Centering Vise for CNC: AR155-I vs AR155-II Selection Guide
A pneumatic self-centering vise grips a workpiece from both sides with shop air, holding it on a fixed centerline so it returns to the same centerline every load. No wrench. No re-indicating. For a high-mix CNC shop, the cost of clamping is rarely the steel; it is the seconds an operator spends walking to the machine, tightening a crank, and proving the setup between runs. The AR155 family from ZPP CNC targets exactly that cost. The AR155-I runs one large part per station; the AR155-II runs two smaller parts in parallel. Both sit on a 155×155 mm footprint that drops onto a TS96 zero point plate. This guide compares the two and works through the air prep, zero point fit, and changeover math that decide if it pays off. To size one, talk to our workholding engineers, or open the AR155-I single station pneumatic vise specs to start.
Key Takeaways
- The AR155-I (single station) holds one part up to 130×145 mm; the AR155-II (double station) holds two parts up to 130×65 mm each — same 155×155×126 mm body, 8–10 kN force, 6–7 bar (87–101 psi) air.
- Rated clamping force is reached at standard shop air (6–7 bar / 87–101 psi). No hydraulic booster is required, unlike competitors that quote peak force at 140–150 psi.
- The 155×155 mm base matches the TS96-155 zero point plate on the 96 mm hole pattern, so both models swap as a unit without re-indicating.
- A spring self-locking mechanism holds the workpiece if air pressure is lost — built for lights-out.
- Per-station cost, not list price, decides single vs double: the AR155-II doubles throughput on parts under 65 mm without adding table space.
What Is a Pneumatic Self-Centering Vise
A pneumatic self-centering vise — UK shops call it a pneumatic vice — is a workholding device that grips a workpiece from both sides with equal force from shop air, automatically centering the part on a fixed datum. It clamps and releases in about 1.5 seconds per cycle, removing the manual crank and the re-indication between loads.
The "self-centering" matters more than the "pneumatic" for most shops. Both jaws travel inward equally from a fixed centerline, so the part lands on the same programmed origin every time. Air just makes that centering repeatable and remote: a solenoid triggers it, not a person. That repeatability is why many shops shorthand it to an air vise — the clamp runs off the line, not a torque handle.
Pneumatic Vise vs Pneumatic Zero Point Module — Know the Boundary
Buyers confuse two tools, so we draw the line. A pneumatic vise clamps the workpiece — it sits on the table and grips the stock you cut. A pneumatic zero point module clamps the fixture or plate, locking a sub-plate or tombstone to one datum. They are partners, not substitutes; for the interface that holds the vise to the table, read our guide to pneumatic zero point modules — the AR155 bolts onto exactly that plate.
AR155 Specifications at a Glance
The two AR155 models share a body and differ only in how the jaw station is divided. Here is the full comparison from the ZPP 2025 catalog (page 31).
| Spec | AR155-I | AR155-II |
|---|---|---|
| Stations | Single | Double |
| Body size (L×W×H) | 155×155×126 mm | 155×155×126 mm |
| Weight | 9.0 kg | 8.5 kg |
| Jaw width | 130 mm | 130 mm |
| Clamping range | 130×145 mm | 130×65 mm (per station) |
| Clamping force | 8–10 kN | 8–10 kN |
| Air pressure | 6–7 bar (87–101 psi) | 6–7 bar (87–101 psi) |
| Body material | Aluminium | Aluminium |
| Jaw material | Hardened steel | Hardened steel |
| Base pattern | 155×155 mm, 96 mm hole pitch | 155×155 mm, 96 mm hole pitch |
See the AR155-I single station pneumatic vise specs or the AR155-II double station pneumatic vise for drawings.
What the 155×155×126 mm Body Means
That footprint decides cell design: at 155 mm square the AR155 takes one TS96 grid position. The aluminium body keeps the whole unit light; the hardened steel jaws are where the bite and wear actually happen.
Aluminium Body, Hardened Steel Jaws
Why aluminium, not cast iron? Every kilogram the robot or operator lifts has to be carried and stopped, so ZPP kept the body under 9 kg. Aluminium stays portable, while the rigidity that matters lives in the hardened steel jaw way and lead screw. For the full range, browse the CNC vise series.
Single Station vs Double Station: Which AR155 Fits Your Parts
The choice between the AR155-I and the AR155-II double station pneumatic vise comes down to one question: how many of your parts fit the envelope at once?
| Factor | AR155-I (single) | AR155-II (double) |
|---|---|---|
| Parts per cycle | 1 | 2 |
| Max part (one piece) | 130×145 mm | 130×65 mm |
| Best for | Large blanks, deep cuts, heavy steel | Two smaller parts, batch, high-mix |
| Table footprint | 155×155 mm | 155×155 mm |
| Throughput (same floor space) | 1× | 2× |
| Typical use | Roughing, thick aluminium, castings | Mirrored parts, fixtures, small batches |
| Choose when | One part fills the envelope | Two parts fit the 65 mm station |
Does Your Blank Fit 130×65 mm?
This is the test shops skip. The AR155-II gives two stations 130 mm wide by 65 mm deep. Measure your raw stock — not the finished part. A 60 mm cube fits; two 62 mm plates side by side do not. A German shop machining hydraulic manifolds was sure the double station wouldn't fit — until they laid out their billet sizes. 70% of their runs were under 60 mm, and the AR155-II doubled those batches per load. The single station wins when one part fills the 130×145 mm window or you are roughing heavy steel and want the full 8–10 kN on one piece.
Counting Cost Per Station, Not Per Unit
The useful number is cost per active clamping station. If parts fit two-up, the AR155-II gives two stations in the same 155×155 mm footprint. For manual two-up without air, a TB255125 manual double station vise covers low-volume work.
Clamping Force and Air Pressure: Where AR155 Beats the Field
The AR155 reaches its full 8–10 kN clamping force at standard shop air — 6–7 bar (87–101 psi). Most competitors quote headline force at the top of their range, often 140–150 psi (≈9.5–10.3 bar), sometimes with a hydraulic booster at over-pressurized air. The AR155 is rated at the pressure your compressor already runs, so you don't need a booster and you're not buying a peak-force number you'll never hit in the shop.
Preparing the Air Supply
- FRL unit on the drop keeps swarf and moisture out and holds the 6–7 bar (87–101 psi) setpoint for consistent force.
- 8–12 mm hose from supply to manifold avoids starving the cylinder on fast close and slowing your 1.5-second cycle.
- Dry, clean air protects seals; a point-of-use dryer pays for itself in seal life.
What Happens When Air Fails
A vise that releases on a pressure drop is a liability in any unattended cell. The AR155 uses a spring self-locking mechanism: the spring drives the jaws closed, air opens them. Cut the air and the jaws only clamp harder. The part stays put, the spindle stops safely, and nobody gets an ejection at 2 a.m. That fail-safe is why the AR155 is safe for lights-out work.
TS96 Zero Point Compatibility: The 96 mm Ecosystem
The 155×155 mm base is sized to seat on the TS96-155 zero point quick-change plate, which carries the 96 mm pull-stud hole pitch. Drop the AR155 on and lock it; the vise and its datum move to any machine as one piece.
Two plates sit under it: the TS96-155 plate (manual quick-change base, fast hand swap) and the AR96-155 pneumatic zero point plate (adds air-actuated locking so the assembly changes on a signal).
Both share the 96 mm pattern, so manual and pneumatic mix on one table. For the broader picture see the TS96 zero point system selection guide, or the pneumatic zero point clamping units range.
Cross-Brand Fit and Expansion
The 96 mm pitch is industry-common, so the AR155 also seats on other zero point plates on that grid. From one plate you build up: a TS96 4-station tombstone for multi-face milling, a tilt base for 5-axis, or several vises on one platter.
Changeover Time Savings: The Vise-Specific Math
A manual self-centering vise needs roughly 30 seconds of cranking per load. The AR155 closes and confirms in about 1.5 seconds on air. At the vise, that is the quickest way to reduce CNC setup time without re-fixturing — the 30 s crank becomes a 1.5 s signal.
Force consistency is the quieter win: manual clamping varies ±10–15% by operator and fatigue, while pneumatic holds ±2–5% cycle to cycle.
For broader context, a vendor-aggregate compilation (not ZPP testing) reports changeover falling 21.4→3.0 min (−86%), spindle use 42%→71%, first-article pass 78%→96%, and $28k–45k saved per machine yearly. XY-GLOBAL cites manual tool-setting 30→3 min with 3–6 month payback; Lyndex-Nikken / A to Z Machine report part-to-part gain above 50% and ROI under six months. AMF reports up to 90% changeover reduction on its own systems. Those are vendor-reported category figures; the AR155's own contribution is the 30 s → 1.5 s cycle and the ±2–5% force band.
One Midwest shop found its night shift wasn't bottlenecked by the cut. It was the operator walking over to load and crank each part by hand — on a 3-axis Haas running 40 mm aluminum brackets.
Pneumatic vs Manual vs Hydraulic: The Real Comparison
| Factor | Manual vise | Pneumatic vise (AR155) | Hydraulic vise |
|---|---|---|---|
| Clamp cycle | ~30 s (wrench) | ~1.5 s (air) | 3–5 s (pump) |
| Force consistency | ±10–15% (operator) | ±2–5% (regulator) | ±2–5% |
| Utilities needed | None | Shop air 6–7 bar | Hydraulic pump + lines |
| Automation-ready | No | Yes (M-code) | Yes (retrofit) |
| Best fit | One-off, low volume | High-mix, lights-out | Heavy steel production |
Quick Decision by Volume
- Low volume, one-off, prototype → manual. Lowest entry cost, no air needed. the TB255125 covers manual two-up work without utilities.
- High-mix, lights-out, robot-loaded → pneumatic. A CNC air vise such as the AR155 earns back its air line on reclaimed spindle time and the labor you no longer spend at the machine.
- Heavy steel, dedicated roughing → hydraulic. More force and stiffer structure for brutal cuts, at the cost of a pump and plumbing.
To compare all four vise actuation types side by side — manual, hydraulic, pneumatic, and zero point — see our full breakdown.
Integrating the AR155 Into an Automation Cell
The AR155 is built to be a signal, not a task: an M-code (a program command that triggers the solenoid) feeds or vents the vise so the jaws move — no operator.
These three details make or break an unattended cell:
- Clamp confirmation. Add a pressure switch so the control confirms the part is seated before the spindle starts, or you will eventually cut air.
- Cobot payload. Keep the combined mass — 9.0 kg (AR155-I) or 8.5 kg (AR155-II) plus pallet and part — inside your robot's payload with margin for acceleration forces.
- Chip and coolant management. Mount the vise so the air port faces away from the coolant stream; add a purge line if you flood heavily.
Jaws, Clamping Range, and Workpiece Mounting
The AR155 runs a 130 mm jaw width. The hardened steel master jaws take the abuse; on top you fit soft jaws — hard jaws for consistent geometries, machinable soft jaws (aluminium or mild steel) for irregular or thin-wall work that distorts under serrated hard jaws. Measure the raw billet, not the finished part; the 130×145 mm (AR155-I) and 130×65 mm (AR155-II) windows are for the stock you load.
Where the AR155 Pays Off: Application Scenarios
Four shops get the most from the AR155:
- Medium aluminium and steel parts in the 130 mm class — the 8–10 kN force handles the roughing without hydraulic mass.
- High-mix job shops that change the part, not the setup.
- Unattended night shifts running on spring self-locking and M-code control.
- Tombstone or 4-axis work, where several self-centered stations swap as one assembly.
As a pneumatic vise for batch production, the double-station AR155-II leads — two parts per cycle on the same footprint.
5-Step Selection Process
- Measure your part envelope. Lay out the billet. Under 65 mm deep and you can likely go two-up on the AR155-II; over 145 mm and you need the single station.
- Confirm your air quality. Clean, dry shop air at 6–7 bar (87–101 psi) and an 8–12 mm line. No air, or filthy air? Solve that before the vise.
- Choose single or double station using the matrix above — by parts per load, not by price tag. See the AR155-I single station pneumatic vise specs or the AR155-II double station pneumatic vise for drawings.
- Choose the base. Manual TS96-155 plate for hand-swap cells; AR96-155 pneumatic plate if you want the plate itself to change on a signal.
- Cost per station. Divide your spend by active clamping stations and by parts per hour. That number, not the catalog price, tells you which model is the better value. If you want the best pneumatic vise for CNC milling in the 130 mm class, the AR155 pair spans single and double station on one TS96 grid.
A small shop owner we advised skipped step 5 and bought the single station by habit. Once he counted stations per hour on his 55 mm brackets, the AR155-II paid for itself in the first month of two-up batches.
AR155 Pneumatic Self-Centering Vise FAQ
What air pressure does the AR155 pneumatic vise need?
Standard shop air at 6–7 bar (87–101 psi). The vise reaches its full 8–10 kN rated clamping force across that whole range — no booster required.
What clamping force does it deliver on steel vs aluminium parts?
The 8–10 kN force is set by air pressure, not by the workpiece material. Aluminium body and hardened steel jaws mean the vise stays light (9.0 / 8.5 kg) while the steel jaws deliver the grip and wear life on any stock.
Does the AR155 hold the part if shop air fails?
Yes. A spring self-locking mechanism drives the jaws closed; air is what opens them. On air loss the jaws only clamp harder, so the workpiece stays put — safe for lights-out and robot-loaded cells.
Does the AR155 fit standard 96 mm zero point plates?
Yes. The 155×155 mm base follows the 96 mm hole pitch and seats on the TS96-155 plate (manual) or the AR96-155 plate (pneumatic). It also fits other zero point plates that use the same 96 mm grid.
Can I run two AR155 vises from one solenoid?
You can zone multiple vises off one solenoid and one air manifold, provided the line diameter (8–12 mm) and flow support the combined cylinder volume. For independent control, give each vise its own solenoid so programs can sequence them.
What is the difference between AR155-I and AR155-II?
The AR155-I is single station, holding one part up to 130×145 mm. The AR155-II is double station, holding two parts up to 130×65 mm each. Both share the 155×155×126 mm body, 8–10 kN force, and 6–7 bar (87–101 psi) air.
Can the AR155 be used on 4th and 5th axis work?
Yes. The low 126 mm profile and 155 mm square base suit 4th-axis platters and tombstones. For 5-axis, mount on a tilt base or tombstone so the part stays accessible; self-centering keeps the datum on origin each load.
Is a pneumatic vise worth it for a small job shop?
If you run the same part more than a few times a day, or you want to cut unattended, yes — the 30 s → 1.5 s clamp cycle and removed labor usually pay back within months. For truly one-off prototype work, a manual vise is the right start.
How fast does the AR155 clamp and release a part?
About 1.5 seconds per clamp or release cycle on clean shop air at 6–7 bar (87–101 psi), versus roughly 30 seconds of manual cranking on a hand vise.
What air preparation does a pneumatic vise require?
An FRL unit (filter-regulator-lubricator) on the drop, an 8–12 mm supply hose to avoid starving the cylinder, and dry, clean air to protect the seals. A point-of-use dryer extends seal life in humid or unheated shops.
How consistent is the clamping force cycle to cycle?
Force tracks the air regulator, holding ±2–5% from cycle to cycle. Manual vises vary ±10–15% by operator and fatigue.
Can the AR155 be driven by an M-code and run lights-out?
Yes. An M-code triggers the solenoid that feeds or vents the vise, so clamp and release run inside the CNC program with no operator. Add a pressure switch for clamp confirmation and the cell can run unattended.
Ready to put an AR155 on your table? Talk to our workholding engineers and we will size the single or double station model to your parts, your air supply, and your zero point plates — or open the AR155-I product page and AR155-II specs to check the drawings yourself.