Compressed Air Couplings

[Bill PhinnParticipant @billphinn90025]

I’m planning to buy a compressor – probably either the 24L or 50L from the Hyundai ‘“Super Silent” range.

My understanding was that these have Euro couplings.

In preparation I bought a pack of couplings off Amazon that were described as “Euro hose fittings”.

They have arrived, and you can see three of them together in one of the photos below. My understanding is what they are in fact are PM20 fittings (they do have a 1/4” BSPT thread). I don’t know how common PM20 fittings are and in which countries, but they don’t appear to be that common in the UK, which seems to use mainly either PCL Standard or EURO fittings.

My understanding is that a Euro fitting is what you can see on the end of my tyre inflator (from a cheap and hideously loud Aldi compressor).

Could someone confirm what I’m saying or put me right?

Lastly, is there any difference between a EURO fitting and a EURO XL fitting or do they describe the same thing? The AI I’ve consulted says they are different but non-AI sources I’ve consulted suggest otherwise.

[Bill Phinn]

On 20 January 2026 at 16:21 Bill Phinn Said:

My understanding is that a Euro fitting is what you can see on the end of my tyre inflator

I would also know this as a Rectus fitting. Many brand names make their own product line, called by its own proprietary name, which are dimensionally identical.

See this thread, which may also have a name for the group of three:

https://www.mig-welding.co.uk/forum/threads/what-are-these-air-fittings.147365/

[Adrian R2Participant @adrianr2]

Played that game. There are far too many variants, some the same with different names and not all fully compatible (or I may have been unlucky). When you find a type you like buy as many as you think you will need for your workshop plus a few spares from the same supplier in one go and save thinking about it again.

https://en.wikipedia.org/wiki/Air-line_fitting

[DC31kParticipant @dc31k]

The Wiki page above is a good reference for the types.

Looking at the table therein, Rectus has entries in the most rows, so a copy of their technical catalogue would give you most bang for your buck if dimensions are required.

[Clive FosterParticipant @clivefoster55965]

If still within the Amazon returns window best to send them back. Obviously not Euro and, if so described by the maker/supplier, they clearly don’t know what they are selling so no telling what they actually are. Assuming they are to a recognised standard at all.

I’ve been asked to identify nicely finished “China Inc” parts and failed miserably. Looked the part but not quite right and would not have connected properly. Still got one very similar to your second picture floating around somewhere. As I recall things the taper and parallel part at the end were mis-proportioned.

Frankly PCL is still the safest low cost purchase even though economy range kit tends to be Euro now. I’ve yet to find a PCL that didn’t fit well. Some of the security latched ones fit too darn well actually! PCL doesn’t flow as well as Euro style tho’.

Economy Euro style can be a lottery. No name Amazon, E-Bay et al varies from very decent to “how does it hang on”. The LiDL ones I hoovered up a while back in preparation for switching to all Euro style from a mix of Euro & PCL were uniformly excellent at half brand name price. (Predictably the switch over got no further than getting the parts!)

I think best option right now for Euro is the PCL-XF range sold by Screwfix at an attractive price. Usefully less flow resistance than standard Euro, about 20% I think, for no more money than standard from many suppliers and a known brand. In the quantities a normal Model Engineer / Home Workshop person is likely to need the extra cost relative to uber economy Amazon / E-Bay et al is hardly significant.

Clive

[noel shelleyParticipant @noelshelley55608]

Go with and stick with PCL ! What you have looks like a cheap, plated diecast unit. Available at most good motor factors Etc.  Noel.

[noel shelley]

On noel shelley Said:

What you have looks like a cheap, plated diecast unit.

Please share your expertise with us and explain how we could distinguish a diecast unit from one that is not so.

[DC31k]

On DC31k Said:

On noel shelley Said:

What you have looks like a cheap, plated diecast unit.

Please share your expertise with us and explain how we could distinguish a diecast unit from one that is not so.

I would have thought someone with your knowledge could have seen the parting line down the middle where the two halves of the die formed the casting. Great source of airleaks.

Lidl ones work for me.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, PCL couplings are a trade name PCL. these types are used widely in industry in Briton, the photo below shows four quick release male couplings, and from left to right are; PCL, Neilsen, both of them are steel, a unbranded chrome plated steel euro type, and a unbranded brass euro type. The euro type are very often used on DIY compressors and airlines. I do think the PCL and Neilsen type are much more durable in situations where they are coupled and uncoupled frequently.

 

Regards Nick.

[noel shelleyParticipant @noelshelley55608]

Thank you Jason, I was going to suggest a magnet. In a busy workshop brass or the cheap diecast even worse will very quickly get damaged and leak. The die cast ones have little strength and can easily snap off, A flailing air line is a dangerous thing.   I seem to think PCL type are hardened or of tough steel. Though for many applications 1/4″ is fine there are both 3/8″ and 1/2″ types, I use a 1/2″ on the big air gun.  Noel.

[Colin HeseltineParticipant @colinheseltine48622]

I have always used PCL and still have the same hoses with the same connectors as I built up in early 1970’s.  They always clip together easily and dont leak.  So thats over 50 years of use.  My rubber airline hose is starting to show a few cracks but the connectors are great.

Colin

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Colin, if your hose is showing cracks, you ought to think about changing it, as Noel Shelley has pointed out, a burst hose is dangerous, and will fly about like a crazy snake that’s lost it’s mind, and you’ll have a job to try and catch it, and they do burst without any warning sometimes.

Regards Nick.

[Bill PhinnParticipant @billphinn90025]

Thanks a lot for the replies.

The Amazon fittings are on their way back, and I nipped to Screwfix to get some of their PCL XF (aka Euro) fittings instead. Thanks for the heads-up on that one, Clive.

I’m not sure how much of an issue it would have been (because I wasn’t in a position to test them) but the cast fittings from Amazon all seemed to have a burr around the outer perimeter of the ends (I mean the ends that were no good to me because they were PM20 style).

Even though I’ve got PCL XF/ Euro fittings for now, I’ll be interested to try PCL standard fittings for comparison at some point.

Just considering a decent blow gun now. The market seems to be flooded with cheap die-cast ones that I’m not sure would be my best bet. I’m looking at PCL branded ones and a set by Laser (code 7835). Unfortunately, my Screwfix didn’t have any of the PCL branded ones they advertise in stock.

[Grindstone CowboyParticipant @grindstonecowboy]

Don’t go for a plastic PCL blow-gun, I bought one a while ago and it was very fragile – the trigger/handle broke off the first time it was dropped. Yes, I know, but these things happen. Edit – it was the BG5002 model sold by Screwfix (although not bought from them).

A Lidl/Parkside die-cast one that came in a set with a tyre inflator was a lot better.

Re air hoses bursting, had one do that to me earlier this year. Luckily it burst just by the coupling connected to the tank so nothing flailing around, but the bang happened just as I was lowering a car on a trolley-jack, and it darn near gave me a heart-attack. Wasn’t my compressor, though, was just using a friend’s workshop. 🙂

Rob

[not done it yetParticipant @notdoneityet]

Rob,

Was your friend called Dave, by any chance.🙂

[Grindstone Cowboy]

On Grindstone Cowboy Said:

A Lidl/Parkside die-cast one that came in a set with a tyre inflator was a lot better.

🙂

Rob

That’s essentially what I’ve got already. I’ll try getting by with that to begin with.

[OldironParticipant @oldiron]

PCL is the way to go. Very durable. Easy to connect and disconnect under pressure. Available every where.  I would not use anything else.

[Grindstone CowboyParticipant @grindstonecowboy]

Best connector I have come across was years ago, not sure of the make but it fitted standard PCL so may have been made by them. Really easy to connect/disconnect under pressure, which I find the Euro ones are not. What was different was that you rotated the sleeve slightly rather than sliding it back – it wasn’t a bayonet fitting like the PCL InstantAir range though.

Rob

[Bill PhinnParticipant @billphinn90025]

Bit of an update on the Hyundai compressor I said I was buying. I received a 50l one a couple of days ago in a very distressed and torn open box. Fortunately the only damage that appears to be done is the plastic switch cover/actuator that the manual says you are to use to turn the machine on and off with. This was sheared off in transit and the result can be seen in the phots.

I’ve asked for a replacement part to be sent out. They replied that they haven’t got a replacement part in stock and I’ll have to package machine up, be in for a collection and then be in for a re-delivery of a replacement machine.

Problem is, the box was virtually destroyed by the courier, incl. the polystyrene inside, and the machine would almost certainly not be protected properly if it was sent back in that box. I’m also very reluctant to take two more days off work to be in for two more courier visits. I’ve pointed all this out to them. Waiting for an answer.

Under the circumstances is it unreasonable of me to ask that they take the affected part off a new machine and send me that? Problem would then be resolved. Once the part is in stock they can put that on the new machine and sell it as intended.

What would you want or ask for? The machine seems to work fine in spite of the absence of the flimsy non-functioning plastic part and the inconvenience of having to turn it on and off at the wall.

[Richard BParticipant @richardb44403]

Did you buy direct from Hyundai?

I did and mine was also damaged – the box and packing were good so had received some punishment.

They sent me a label and as mine was the smaller size I dropped it off at the Post Office. You may need to drop off elsewhere with a larger model but avoids waiting for couriers.

Seems for warranty etc you have to start with a unit in original condition as they were concerned there may be unidentified damage. Hence safety issues etc.

 

They do a kit of accessory tools that seemed good value for money.

The machine is quiet and whilst I only use it occasionally it seems good.

[Bill PhinnParticipant @billphinn90025]

Thanks, Richard. I’ll mention the possibility if necessary of dropping the old one off. It was bought directly from Gen Power.

I’d be interested to know what the law says about the consumer’s responsibility for packaging up a return securely when the original packaging arrived unfit for purpose and for re-use, and the packaging is unavoidably so large that a consumer couldn’t reasonably be expected to supply adequate alternative packaging.

 

[JasonBModerator @jasonb]

Mine has worked fine for the last couple of years switching on and off at the wall, machine is under the bench so easier to use the switch on the wall socket.

[JasonB]

On JasonB Said:

Mine has worked fine for the last couple of years switching on and off at the wall, machine is under the bench so easier to use the switch on the wall socket.

Having had an allegedly decent breed of 13A socket switch weld its contacts together on a lighter load than Jasons compressor around 15 or 20 years ago I’m more than ever convinced that switching high inrush current loads through common fixed to the wall switchgear isn’t a wonderful idea. Dissecting that particular switch revealed painfully inadequate contacts and a “less than fast” operating mechanism. The cooker socket installed at the same time by the same electrician has also welded itself together sometime in the last half decade or so. I’ll deal with that when the cooker dies. According to Mr Electrician these were a premium brand but a bit cheaper than MK at trade prices. The invoices suggested 10% less.

For me anything with a motor gets either a proper DOL starter or VFD. Not in love with those combined pressure regulation and pull / push on / off switches. Even the factory fit one on my Hydrovane 502 doesn’t exude the strength and durability I’d ideally expect from industrial machinery. But with a DOL starter installed at the same time as the compressor it got turned on about 20 years ago when the compressor went it and is unlikely to be touched again until the executor disburses my workshop!

Some of the bottom end of the range ones can be frightening flimsy. Doesn’t give a warm fuzzy feeling of safety when the thing wobbles and casing flexes as you operate it.

Personally in Bills position I’d splash out on a decent industrial rated equivalent and do a decent job of fitting with a robust bracket. As Jason and others have found the compressors themselves are effective and, in home workshop terms at least, long lived.

Clive

[Adrian R2Participant @adrianr2]

Apparently there are better sockets available now as they are needed for electric vehicle charging, might also be good for workshop use. Look for ones manufactured to BS1363-2 and marked EV on the back.

I’m not a sparky so I don’t know whether it’s acceptable just to swap them over onto existing wiring but if you are running bigger loads then worth considering.

 

[Bo’sunParticipant @bosun58570]

A bit of an aside I guess.  I use the Euro style connectors, but also have a couple of PCL ones kicking around.  The Euro fittings have a larger thru’ bore then the PCL ones, is this the norm?

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