Axial Pressure Gauge 0–12 bar — 40 mm Dial, G 1/8″ Male, Compact, for Compressor

Ø40 mm G 1/8″ vs Ø50 mm G 1/4″: When You Need This Smaller Size

This is the most compact standard size of axial pressure gauge for industrial pneumatics. The difference is critical when ordering:

When to choose Ø40 mm G 1/8″:

• 1/8″ size mini pressure regulators (Festo GRLA-1/8, SMC AR10/AR20, Norgren 11-018)
• Low-pressure precision systems (0.5–8 bar) with compact units
• Built-in panels with limited gauge mounting space
• Secondary pressure monitoring points in branched pneumatic circuits
• Robot pneumatics — compact air pressure regulators on each gripper arm

When Ø50 mm G 1/4″ is the right choice:

• Standard FRL units (Festo LFR, SMC AW30/AW40, Parker B07)
• Primary pressure monitoring stations at workstations

⚠️ Do not confuse G 1/8″ with G 1/4″ — these are different thread sizes. G 1/4″ has an OD of ~13.2 mm, G 1/8″ is ~9.7 mm. Trying to fit a G 1/4″ gauge into a G 1/8″ port is physically impossible. A G 1/8″ gauge in a G 1/4″ port will enter but rattle and leak. Check the thread before ordering.

What G 1/8″ Means in Pneumatics

G — designation for parallel pipe thread to ISO 228 (BSP — British Standard Pipe).

1/8 — nominal size in inches. This is not the actual pipe or thread diameter — it is a conventional size designation:

Technical Specifications

Full Axial Gauge Range Available at Acvatron SRL

0–12 bar Scale: Choosing the Right Range

Selection rule: working pressure should equal 60–70% of full scale.

For mini-regulators typically set to 2–6 bar output (instrument air for precision tooling), a 0–6 bar scale gives a more legible needle position. The 0–12 bar scale is a universal choice when inlet pressure is up to 8 bar and the regulator operates across a wide range.

Where the Ø40 mm G 1/8″ Gauge Is Used

Mini-regulators and micro FRL units Festo LR-1/8-D-MINI, SMC AR10, AR20, and similar compact 1/8″ regulators have a G 1/8″ Female port for a built-in Ø40 mm gauge. This gauge is a direct replacement.

Precision pneumatic automation systems Small pneumatic systems with fine pressure adjustments: test rigs, laboratory equipment, precision spray systems.

Compact control panels Where there is no space for a Ø50 mm gauge — Ø40 mm fits into a denser panel layout.

Secondary pressure monitoring points On branched pneumatic circuits — pressure monitoring after each regulator in each zone. The compact Ø40 mm allows more monitoring points on the same panel area.

Robotic systems and manipulators Small air pressure regulators on each manipulator arm — Ø40 mm is optimum for the available space.

Installation: Key Points

PTFE tape is mandatory G 1/8″ is a parallel BSP thread — it does not seal by taper interference. 2–3 wraps of PTFE tape or a drop of anaerobic sealant (Loctite 542 or equivalent) — mandatory for every installation.

Bleed pressure before replacement Always bleed line pressure to zero before unscrewing the gauge. The small G 1/8″ size has a smaller seating area, but 6–8 bar pressure will still eject the gauge with a sharp bang.

Tightening torque G 1/8″ thread is sensitive to overtightening due to its small diameter. Tighten by hand with a light spanner assist — 10–12 N·m. The plastic gauge body will crack under excessive force.

Axial connection — panel mounting orientation When mounting in a panel, ensure the cut-out matches the Ø40 mm body OD. Use the gauge’s retaining nut for secure panel fixing (if provided in the regulator design).

Expert Opinion

“G 1/8″ Ø40 mm is a specific size needed for a specific piece of equipment. The most common mistake: someone comes in saying ‘I need a small gauge for a regulator’ and picks up a G 1/4″ Ø50 mm because that’s what’s on the shelf. They take it back, try it — it won’t fit. The reason: 1/8″-sized mini-regulators have a G 1/8″ port, not G 1/4″. The physical difference is easy to see: the OD of the G 1/8″ thread is about 10 mm, G 1/4″ is about 13 mm. Second point: a 40 mm dial reads well at arm’s length — for a built-in regulator that’s enough. If the gauge is mounted on a panel viewed from 1.5–2 metres away — go for Ø63 mm.”

Vitaly Boluchevsky, Chief Engineer at Acvatron SRL, 15 years in the industry

FAQ

❓ Can a G 1/8″ gauge be fitted to a G 1/4″ port? No. G 1/8″ is smaller than G 1/4″ — it will enter the G 1/4″ port partway but will not seat correctly and will leak. For a G 1/4″ port you need a G 1/4″ gauge. If needed — use a G 1/8″ Male to G 1/4″ Female adapter.

❓ What size is my Festo GRLA-1/8-QS-6 regulator? GRLA-1/8 is a G 1/8″ size regulator. The gauge port is G 1/8″ Female. This G 1/8″ Male Ø40 mm gauge is a direct fit.

❓ Is PTFE tape needed? Yes, mandatory — G 1/8″ BSP is a parallel thread and does not self-seal. 2–3 wraps of PTFE tape are sufficient for reliable sealing at pressures up to 12 bar.

❓ Is a similar G 1/8″ gauge available with a 0–10 bar or 0–6 bar scale? Check availability with an Acvatron SRL manager: +373 22 503-580. For precision systems with pressure up to 4 bar, a 0–6 bar scale is recommended — the needle sits in a more readable position.

❓ What is the difference between G 1/8″ and NPT 1/8″? G 1/8″ is a parallel thread (BSP — uniform diameter throughout). NPT 1/8″ is a tapered thread (narrows toward the end) — the US standard. They look very similar but are not interchangeable. NPT seals on the thread taper; G requires PTFE tape or sealant.