Brass vs Steel Air Compressor Fittings

I notice a curiosity while browsing the local hardware store. The same air compressor fitting is available in steel and brass, but the steel one is a couple dollars less expensive. Since both seem perfectly functional, what’s the motivation for the more expensive brass version?

It won’t rust and it will seal at the threads.


I can understand the better corrosion resistance, but brass yields a better “seal at the threads”? Why would that be?

Because it is more ductile than steel and when tightened brass will “gall” in a good way, providing the sealing effect. I always teflon tape the threads anyway… but thats just me.

Do yourself and your air tools a favor and buy brass.


I have used both. The steel is zinc coated or plated, depending on supplier and is pretty tough. The brass seals better but can be damaged more easily than the steel. The steel will seal with the right sealer. I generally use teflon pipe dope for both.

Brass, as a material is more expensive than steel.


It’s softer.

For me it was always the more convenient alternative because it could be easily attached and sealed then disconnected and attached to another fitting and sealed tightly with just firm twist.

I think I have both. The quick connects are mostly brass but the male fittings are mostly steel. Probably something I’ll look for next time. You can never have too many fittings.

The main thing to watch on the quick connects is that they aren’t all equal. Even if you have 2 steel ones, the shank can be different, so one of them won’t fit in the female coupler. It’s annoying when you need to replace one and don’t remember which you have.


Concur. I always take a male fitting with me to make sure. I pretty much just get them from the farm store now but they have several different ones on the shelf.

Oh yeah now I remember someone was talking about getting the fittings with the larger hole so as not to restrict air flow. I knew there was something, just couldn’t remember what the issue was till I looked at my Amazon views history.

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Mr @shadowfax brings up a very good point (as usual) with the mention of the fittings having different profiles. It truly can get maddening at times as there are quite a few variants out there. Its usually only a problem when you are over a friends shop or work space and you have an intermingling of different peoples air tools… inevitably somebody’s something wont fit into the receiving end and the dreaded plug swapping begins… This for some reason is high on the list of things that absolutely bother me to no end… excuse the pun there.

It would be nice if everyone used the same fitting, I use “M”

I believe top row is for 3/8 line
and bottom row is 1/4 line

I bought a lifetime supply around 25 years ago. A buddy was a rep for quite a few companies and CEJN was one. They were expensive compared to most but well worth it. They have still one of the best designs for least amount of flow and pressure loss. I only had one that got hard to move the collar in all that time and use. It’s made to be taken apart so I cleaned it all up, lubricated and it’s like new again. Buy good ones, buy them once.

A McParts store was changing sources for fittings many years ago and for a few $ I bought a 5 gallon bucket full and sorted them out eventually. I still have a few pieces and including a good collection of compression fittings that I hold onto for some reason.

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