Advantages to different air coupling types?

When I started my air tools collection a few years back I went with the "automotive" type couplers. Guy at the bearing store said they were best, so that's how it started. They work fine for me, but most of the tools I buy used come with the "industrial" fittings. It's getting to I'm spending a certain amount of money replacing them. I don't like the universal female connectors.

So what's the deal? Do I stick with auto types, or retool for industrial? Any advantage to either one over the other?


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You can make up an adapter from 2 fittings (or 2 fittings on a short section of hose) if you have 2 styles to use. Changing the male fittings for the tool port is another way to go.

WB ............

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Wild Bill

Industrial with the larger bore is the way to go. The automotive ones suck, IMO.

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For the mopst part I don;t have a problem with the standard 1/4" bore automotive types. Most of my problems were with the female couplers always developing a leak. I used good quality couplers, and still they would leak after some use. Seems like tools like my air grinders and some sanders made the couplings vibrate, which led to making it leak. My solution was to remove the male connection at the tool and add a hose barb, and a 3 foot piece of hose that was attached to the male coupling. Yea, I know nothing like having a "extension cord" dragging around on a tool, as we are usually accustomed to having just an air tool with connector and no cords or hoses attached, but since I added these short extensions of hose to the tools my leaks have virtually dissapeared. I use Aero Quip or Foster air hose connections for 1/4" hoses for the most part, and on really long hoses I use a 3/8 or 1/2" hose with adapters to fit my regular 1/4" hose.

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Here in the Seattle area a lot of guys just use what is sold at Boeing Surplus. They use "industrial" and you can get it in 1/4", 3/8" and 1/2" sizes. The best female couplers are the kind you have to turn, pull and turn again to release - they vent the air slowly and controllably and there isn't that big snap of released air and the whipping of the downstream hose exhausting its pressure. Can't remember the brand right now. I told the guys in the lab where I used to work about them and when the lab moved they retrofitted to the cool fittings and those guys were absolutely ecstatic. Complete one-hand operation, no squinting up your eyes in fear.

I gave up on the auto stuff years ago. I don't think it's intrinsically any worse than the industrial, but I think there may be a lot of el cheapo stuff out there. As always, you get what you pay for. I'm lucky - I think I'm done buying air tool fittings!

Grant Erwin

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Grant Erwin

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David Billington

The turn-slide-turn is Dynaquip, where it depressurizes the downstream line before the coupler separates.

The other style at Surplus is Parker, those are nicer because you can just push the male end into the coupler, no need to hold back the ring. They also have a rotating collar to close the vent and open the line.

Uncoupling a pressurized 1/4" hose is one thing, uncoupling a pressurized

1/2" line is another altogether so I see why they use these.

Surplus has at least 4 completely different styles of pneumatic fittings alone, and I don't just mean different sizes but completely different geometry. I think it's "industrial", "automotive", "schraeder" and the fourth is a slimmer plug between the first two in shape. Then about 4 more styles of hydraulic couplers.

I figure in part they use the different styles for dry air, oiled air, breathing air ... to keep the air sources and the hoses straight.


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