Compressed Air Fitting Forum

Do you have a compressed air fitting question? This is the fitting forum page were you can post your compressed air fitting questions and myself, plus our very knowledgeable visitors, will take a stab at answering it for you.

Before adding a new questions I would appreciate it if you would first read the Fittings page as I have tried to include enough information on those pages to answer pretty much every compressed air fitting question I could think of. There are also a bunch of questions received and answered below the form near the end of this page.

If you check there or on the compressed air fitting page first you may find an answer to your fitting question right away.

If you cannot, then know that there are lots of the half-million visitors or so to this site every year that know a lot about air fittings, so please, use the form below to ask your question about fittings, and all of us will see if we can come up with an answer for you.

Others will benefit from the answer to your question too, I'm sure. If you spot a question you can answer, why not do so by making a comment?



Compressed Air Fitting Question

Having an issue with compressed air fittings? Ask away.

Visitor Compressed Air Fitting Questions

Please see other questions and answers below.

What type of male connector?  
I have connectors on my nail guns that must be of an older style than the ones I see these days. Mine have a rounded inset that locks into the female …

I need to know a tap size to reduce a fitting. 
I have a compressor which needs a fitting replaced, as it has snapped off, and I have been unable to extract the broken brass threaded piece. My …

How do small ID connectors impact CFM/PSI? 
I am working on a basic 2 drop system for my 60 gallon single stage compressor (135psi, 12 CFM @ 90PSI, with a 1/2" output orifice). And I am getting hung …

Air line connector 
My son purchased tools from overseas (China) and is unable to connect it to the air compressor coupling. The connector's threads is 7/16 OD v. std 1/2" …

Tap size for a 1/4 inch air fitting? 
what size tap is used to tap a hole for a 1/4 inch air fitting?

What is orifice dia for a 3/4 npt male fitting? 
what is orifice dia for a 3/4 npt male fitting?

Need tubing kit for 5z185a 
Need to replace tubing from compressor head to tank. Does it come premade for 5z185a? Where could I find it?

Adapting US fitting into metric male fitting 
Adapting US mail fitting into metric male fitting to go into a quick release female fitting in and air compressor. Hello, I purchased an air compressor …

1/4 pipe thread connection 
trying to install a regulator to the second line off my compressor. all the fittings before the line are 3/8. after the TEE 1/4 pipe thread to both hoses. …

Air lines and NPT fittings. 
I have a brand new 33 gallon Husky air compressor and want my tools to get the most out of it. When I bought it I made the mistake of picking up the …

Why 3/8 hose with 1/4 fittings? 
Mostly I see a variety of these offered in local stores (hardware, automotive, etc), versus 1/4 inch hose or 3/8 hose with 3/8 fittings. I've tested the …

Different flow rates between fittings. 
I have always run 1/4 inch fittings, its what my compressor came with and recommended be used. But as I've gotten bigger and more powerful air tools …

Proper hose for Dewalt D15546 
Basic question here but I am having trouble finding out what hose to use for my Dewalt D15546. It appears to have non threaded female adapters (factory …

Are there different kinds of 1/4" NPT quick-connectors? 
I have a "Tool Shop" 20 Gallon compressor from Menards and 1/4" color-coded quick-connects from Farm & Fleet, but the connectors won't go into the quick-connect …

Airline Connector 
Hi, I don't know if you can help me with this? See attached, what is this sandblasting airline connector called?If I know what its correct name is I can …

New 1/2 inch Hose with old 3/8 inch quick-connects 
I just bought a 1/2 inch hose with 1/2 inch npt-18 fittings. My compressor is set up for 3/8 inch. What adapter do I need to use my 1/2 inch hose with …

Air manifold and air distribution 
Is there a compressed air manifold that distributes the air evenly from each outlet?

Rol-Air hasn't got hose connectors 
I just bought a new 20 gal. compressor from Rol-Air and there are no connections for air hoses. Do you have a diagram sheet that will show me how to add …

How do I know if I have a non-relieving air coupler 
My manual states that I should not use a non-relieving air coupler on my nailer. I bought a set of 5 couplers and fittings for my snap-on nailer. How …

Air tool military quick couplers 
Until recently, I worked as a contractor for the military. In all of our shops, the air outlets accepted a particular type of coupler which I've never …

Connecting a hose reel 
I have a hose reel 3/8"I.D. that I want to connect to my compressor. Do I need any special type of fittings on the ends of my pig tail hose? __________________ …

Where to buy metric fittings for pneumatic finish nailer 
I purchased a duofast finish nailer and I believe that the threads are metric. A 1/4 NPT air hose coupler does not seat well. Where can I buy the correct …

Compressed air compression fitting size 
Compressor Pump Only Speedaire/Granger Part: 5Z405 The outlet is at a Tee. the pipe going into it is 3/4" O.D. What is the fitting that I can use …

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Fittings that will not work with PT fittings?

Question: My pressure regulator has a fitting that will not work with PT fittings. It has a nut that swivels and needs something with threads that will "bottom out" to close the connection. I don't see anything except PT fittings. Where do I get a fitting like this and what are they called?

Response: Interesting, Terry. Itight be a proprietary fitting, but that's not too likely. I take it that the NPT fitting can't be threaded in far enough to form a seal on the threads but it will actually thread in a ways? I wonder if your regulator is actually threaded for a metric fitting? That being the case, you would visit a fitting supplier and ask for a G type fitting? That is one that is designed to thread in and bottom on the boss of whatever it is being threaded into, and seals with an O ring or gasket instead of thread-to-thread sealing. There are some companies that manufacture a shortened NPT thread (Camozzi was one) that might work in the boss too.

Is there a minimum of threads that a
       fitting had to be screwed in? (e.g. half way in, or what fraction of inch)

Question: This a newly installed, permanent compressor. The thread deapth in the unions along the air line are all different; some show two threads left, other six or more. The installer used Teflon tape in all the joints.

Response: Herman, depending on the type of fittings, the thread depth may vary. You aren't saying what air line you are using. I'll guess it's black pipe, yes? That means that the pipe has to have threads cut into it with a die, and that process is slow and exhausting for a large pipe installation. That may be the reason for the variance in thread length, and thread insertion.

You tell me how many threads are showing outside of the female boss, but you don't know, or aren't telling me, how many threads are actually turned into the female boss. That's the critical issue. Spray test the suspect fittings with a bit of dish soap and water to see if any air inside is bleeding out. If the fitting isn't in far enough, you will have quite a leak from a pressurized line, believe me. And if it were my plant, I'd take a properly sized wrench, and using modest force, would try to tighten the suspect fittings another turn or too, just to be sure, although if they don't leak, that might be a waste of your time.

Metric to Standard Adapting Fittings?

Question: I have a 8mm x 5mm supply tube coming off of my compressor, and want to adapt it to my rapid air system. Can 8mm x 5mm be adapted onto Standard straight fittings? (i.e. tube into instant-connect, which has 3/8" male thread on other end)?

Response: See the pages on Fittings for complete info, Brandon. Yes, you will have to acquire an adapter with metric on one side, and NPT on the other. If you use your browser to search, you will find, a number of sources.

Couplers - Do couplers give out?

Question: Do couplers give out? I've taken the hose out from where it stays always and I cannot get it to go back, nor will any of the other connectors. Any suggestions? Thanks, Kelly

Response: Hi Kelly. Well... they are massed produced, and often come from a foreign land with the metal content being suspect, yet I have never worn out a coupler.

What I suspect has happened is that a connector that was inserted into your formerly operating coupler had some contamination on it (likely grease with floor crud maybe...:-) and that crud has transferred inside the coupler and is preventing proper operation.

You might try a solvent (varsol - paint thinner) bath to try and clean it out. If no luck, it's time for a new coupler.

Just make sure that the connector you are using is the same make or configured to fit the coupler.

Sizing NPT fittings enhance Airflow?

Question: I'm finally pluming my shop for air distribution. This site has a lot of great information and if your book is half as good as the web site, it will be great. (I plan on buying a copy soon). Thank you!

My setup: I have a big 2-stage 80 gallon, 4hp, 175 PSI, 12.5 CFM compressor. It has a 3/8 outlet port that I expand immediately (after a ball valve) to 1 inch copper pipe that is sloped 1" to 10' which rings my shop.

Down T's to drains at low points. Up T's reduce the copper size to 1/2 inch and then to a "return bend" (1/2" u-shaped copper pipe) to down pipes and quick-connects. Then on to various tools for wood and metal work (including milling machines that will use compressed-air vacuum tables for hold-down).

My questions are with respect to the quick connect fittings. The last 2 inches at the end of the copper and another 2 inches entering the tools. My local hardware store sells "Type M" NPT fittings in 1/4 inch and "Type-T" NPT fittings in 3/8 inch. It is my understanding the type T fittings are Automotive and the Type M are industrial.

Most tools are 1/4 NPT and some of my tools state that quick-connect fittings can reduce air flow. So how do I choose coupling fittings to "standardize" my shop on so as to not starve any of my tools that need the greater air flow.

Response: Hello Chuck, nice to hear from you. And yes...the ebook is better!

From the sounds of it, you are doing a bang up job in plumbing your compressed air.

You mention that the discharge on your compressor is a 3/8 outlet port. Is it a 3/8 coupler...what exactly? To me, there is your primary restriction.

Even though you increase the pipe size after that 3/8 outlet with your 1" air main, essentially what that air main becomes is a sort of compressed air receiver. Though, if any of your applications draws more air than can come out of the 3/8 discharge from the compressor though, that you have a 1" main is almost immaterial.

Having said that, a 3/8 compressed air line flows a lot of air, so that may not be a problem.

You write, "My local hardware store sells "Type M" NPT fittings in 1/4 inch and "Type-T" NPT fittings in 3/8 inch. It is my understanding the type T fittings are Automotive and the Type M are industrial."

I had not heard that before. My understanding is the "M" type connectors fit "M" type couplers, the same with "T" type couplers and connectors, and the "P" type, the Aro type, the Milton type, the Swagelock type etc. etc.

For most of us, if it is an industrial versus automotive type fitting is less important that does the connector fit the coupler.

As to the flow restriction of couplers and connectors, many are full flow models, meaning that the inner diameter is the full size of the hose. Therefore, a 1/4 hose (with an I.D. of 1/4") will be the same I.D. as that 1/4" connector or coupler, and therefore, there should not be a restriction on the flow of air through them.

If in doubt, visit your local industrial supplier that supplies industry with their fittings, cylinders and valves. Ask them for their brand that are full flow, and standardize your shop and fitting kits with this brand. Then you will not have a problem.

Using 1/4" fittings with 3/8" quick connects?

Question: I use 3/8" fittings on my shop compressor and I have a portable compressor that uses 1/4" fittings. Is there a fitting or coupler that will allow me to use the 1/4" fittings in my 3/8" quick connects at my shop?

Response: Joe, if you are trying to plug a 1/4" connector into a 3/8" coupler, or the reverse, no, I don't think that's possible.

Make yourself an adapter with a 1/4" connector on one end to plug into the 1/4" coupler, and on the other end of the short length of hose, put a 3/8" coupler. That will accept any 3/8 connectors. Or, the reverse.

Thread adapters from 1/4 to 3/8 and vice versa are a common brass fitting available at any plumbing shop.

Comment: Thanks for the great idea, I'll give that a shot for sure.