Pneumatic fittings
Push-in fittings, quick couplings, compression fittings, nipples and adapters, manifold blocks and silencers.
Fittings are the most numerous parts in a pneumatic circuit, and a single wrong size holds up the whole assembly. We supply fittings, quick couplings, nipples and silencers from stock and identify the thread and size of the part you have together with you. Sending a photo or the measurement you took with a caliper is enough.
Types
Push-in fittings
The tube is pushed in to connect and released by pressing the collet. Straight, elbow, tee, Y and swivel types with plastic, brass and stainless steel bodies.
Quick couplings
Disconnect and connect the line in one movement. Types with a check valve shut off the air when disconnected. For air tools and workbench connections that change.
Compression fittings
Tightened with a nut. More durable connections for metal or rigid plastic tubes and for high temperature.
Nipples and adapters
Change the thread size and type: transition between BSP, metric and NPT, reducers, extensions.
Manifold blocks
Split a single air inlet into several outlets for tidy distribution on the machine.
Silencers
Reduce the noise at the valve exhaust. Adjustable types also set the cylinder speed.
Plugs and blanking caps
Close off unused outlets.
Product images: Pemaks.
How to select
In a push-in fitting the tube is not tightened, it is pushed in: the stainless steel grab ring inside holds the tube and the O-ring provides the seal. The fitting size is selected by the outside diameter of the tube. An 8 mm fitting accepts both 8x5.5 and 8x6 tubing. On the thread side, the fraction in the thread name is not inches: a "1/4 thread" is the thread with an outside diameter of 13.2 mm. The table gives the actual outside diameters of the threads. When we take a size over the phone, we match it against this table as well.
If the two types of BSP thread are mixed up, the joint leaks. On a parallel (BSPP, G) thread the seal is made by an O-ring or gasket. On a tapered (BSPT, R) thread it is made by the thread itself, and a thread sealant is needed. Forcing a tapered thread into a parallel port damages the thread. Transition adapters are used for the NPT and metric threads found on imported machines.
Body type and material are selected for the environment. Swivel fittings prevent the tube from twisting and extend tube life on moving fixtures. Metal body fittings are used where there is weld spatter, and stainless steel fittings in food and chemical environments. On jobs where we build the circuit together, we plan the fittings together with the tubing route.
BSP thread sizes: which thread is the diameter you measured?
| Thread | Actual outside diameter (mm) | Hex size across flats (mm) | Typical tubing |
|---|---|---|---|
| 1/8" | 9.7 | 14 | 4–6 mm |
| 1/4" | 13.2 | 17 | 6–8 mm |
| 3/8" | 16.7 | 19 | 8–10 mm |
| 1/2" | 21.0 | 24 | 10–12 mm |
The fraction in the thread name is NOT inches: a "1/4 thread" is not 6.35 mm, it is the thread with an outside diameter of 13.2 mm. The fraction is the historical name of the INSIDE diameter of the pipe fitted to that thread when the standard was created. Compare the value you measure with a caliper against this column. Dimensions are for ISO 228 (BSP parallel). On a tapered BSPT thread the diameter changes along the length, and the measurement is taken at the start of the thread.
Frequently asked questions
How do I choose the size of a push-in fitting?
By the outside diameter of the tube. Both 8x5.5 and 8x6 tubing fit an 8 mm fitting because their outside diameters are the same. The inside diameter does not affect fitting selection. It only determines how much air will pass through the line.
I measured 13 mm with a caliper. Which thread is this?
1/4 BSP. The table gives the actual outside diameters of the threads: 9.7 mm for 1/8, 13.2 mm for 1/4, 16.7 mm for 3/8 and 21.0 mm for 1/2. The fraction in the thread name is not inches. It is the historical name of the inside diameter of the pipe fitted to that thread when the standard was created.
What is the difference between BSPP and BSPT?
BSPP is a parallel thread: its diameter is constant along the length and the seal is made by an O-ring or gasket at the end. BSPT is a tapered thread: its diameter narrows along the length and the thread itself makes the seal, so sealing paste or PTFE tape is needed. Forcing a tapered thread into a parallel port damages both sides.
My push-in fitting is leaking air. What should I do?
First remove the tube and look at the cut end: if it is cut at an angle or has burrs, the O-ring does not seat. Cutting it again square to the axis, without crushing it, and refitting solves most cases. If the outer surface of the tube is scratched, that section should be discarded. If all of this is in order, the O-ring of the fitting is worn and the fitting is replaced.
What is the difference between a swivel elbow and a fixed elbow?
The swivel type can rotate on its own axis after installation. Because the direction can be adjusted after the tube is connected, the tube does not twist and it is easier to respect the bend radius. On moving fixtures it noticeably extends tube life. A fixed elbow is cheaper and is sufficient where the direction will not change.
What does an adjustable silencer do?
It is fitted to the exhaust port of the valve. As well as reducing noise, it throttles the exhaust air and so is used to adjust the speed of the cylinder. This is the most practical way of setting speed in a pneumatic circuit.
I do not know the size of my fitting. How can I order?
Please send a photo of the fitting and the tube it is connected to via WhatsApp, together with the thread diameter measured with a caliper if possible. We identify the thread type and tube size and recommend the matching part from stock.
Stock, sizes and part numbers
Sizes in stock, manufacturer part numbers and brands are kept up to date in our catalog. Send us your requirement on WhatsApp or by e-mail and we will quote and ship worldwide.