Air Hose Fitting--Plastic OK?

[npalen]

Have had this coiled hose around for several years but haven't used it because the end fittings are 3/8" MPT which don't play well with 1/4" quick couplers. So I made an adapter out of 1" delrin but wondering about safety.

The OD of the 3/8" internal pipe thread is about 0.700" so that leaves about 0.150" wall thickness with the 1" OD delrin. I understand and appreciate all the caveats about using PVC for compressed air lines but wondering about the worst possible scenario with regard to the delrin adapter fitting.

I realize that metal adapters are available but just trying to minimize the weight at the ends of the hose.

 

[Ford850]

Why don't you get a 3/8" FNPT coupler and screw it directly to the hose?

 

[npalen]

I don't think that such an animal is available, near as I can tell. I see only 1/4" pipe threads available for 1/4" quick couplers and 3/8" pipe threads for 3/8" quick couplers.

 

[fried1765]

I don't think that such an animal is available, near as I can tell. I see only 1/4" pipe threads available for 1/4" quick couplers and 3/8" pipe threads for 3/8" quick couplers.

NOPE!
Adapters are available.
I thought I was going to need some, and found them available on Amazon.

 

[Peter 315]

https://www.miltonindustries.com/:thumbsup:

 

[Ford850]

Milton makes a model number 718 that is 3/8" FNPT for Type M. That's a common one.

 

[Peter 315]

The cheap made in china ones leak or don't last

 

[Ford850]

npalen, I'm sorry I sort of took this off track from your question. It looks like you did a nice job making that fitting. If it were on mine, I wouldn't be worried about it. I would expect any failure would be a crack and leak, which wouldn't be a safety concern. I'll bet that outlasts your hose though. :thumbsup:

 

[npalen]

npalen, I'm sorry I sort of took this off track from your question. It looks like you did a nice job making that fitting. If it were on mine, I wouldn't be worried about it. I would expect any failure would be a crack and leak, which wouldn't be a safety concern. I'll bet that outlasts your hose though. :thumbsup:

Oh, no problem.
I do see this Model 718 but the price shocked me.

3/8" FNPT M Style Coupler | Milton Industries | Miltonindustries.com

I had checked on Amazon and didn't find anything in a 1/4" coupler with 3/8" pipe thread.

I'll go with the homemade adapters and agree that they will probably outlast the hose. I figured someone was going to say that plastic fittings were a death warrant on air lines.

 

[Deere Dude]

I worked in a big factory using brand name air hoses and very good couplings. Over the years I saw or fixed a few hundred of them that either were ripped off, flew off, knocked off etc and hoses just started flying around. Nobody ever got hurt, not that it couldn't happen.

I don't think I would use that system for anything over a hundred psi though. If you got a heavy duty high PSI compressor I would be really careful with that setup.

 

[npalen]

My compressor is set at 150 psi. I had planned to use UHMW for the adapters but only had delrin on hand. I would feel better with the strength of UHMW.

 

[Peter 315]

Oh, no problem.
I do see this Model 718 but the price shocked me.

3/8" FNPT M Style Coupler | Milton Industries | Miltonindustries.com

I had checked on Amazon and didn't find anything in a 1/4" coupler with 3/8" pipe thread.

I'll go with the homemade adapters and agree that they will probably outlast the hose. I figured someone was going to say that plastic fittings were a death warrant on air lines.

Its a pack of 10 about 7.00 each

 

[pmsmechanic]

If your worried about an exploding fitting harming someone just get some heat shrink and install. It won't keep the fitting from exploding but it will contain the shrapnell.

 

[Big Barn]

You did a nice job making that adapter out of Delrin. I can't definitively attest to it strength but I would feel safe using it

Of course I TRY to avoid using adapters or any extra fittings whenever possible. Just extra potential leak points.

Here's a couple of my coiled hoses with (albeit 3/8") couplers.

 

[s219]

Delrin is pretty strong stuff, and stronger than UHMW by 6-9X depending on the property. I suspect it will be fine. We used to machine a lot of parts out of delrin when I worked in a machine shop in the 90s and I really came to like it.

 

[fried1765]

Oh, no problem.
I do see this Model 718 but the price shocked me.

3/8" FNPT M Style Coupler | Milton Industries | Miltonindustries.com

I had checked on Amazon and didn't find anything in a 1/4" coupler with 3/8" pipe thread.

I'll go with the homemade adapters and agree that they will probably outlast the hose. I figured someone was going to say that plastic fittings were a death warrant on air lines.

The Milton 718 is listed for $9.95 on Amazon.
I am not shocked at that price.

 

[npalen]

Delrin is pretty strong stuff, and stronger than UHMW by 6-9X depending on the property. I suspect it will be fine. We used to machine a lot of parts out of delrin when I worked in a machine shop in the 90s and I really came to like it.

Interesting as I didn't know delrin was that strong compared to uhmw. It sure machines a lot better than uhmw. Deburring uhmw can be a real pain.

Edit: I'm seeing 6000 psi tensile strength on uhmw and about 9000 on delrin.
UHMW stretches 300% before breaking compared to delrin at 25% stretch.
That would account for why uhmw can be cold formed perhaps?

 

[bazman]

you can probably find something here Titan Fittings | Stainless Steel Fittings | Stainless Hose Fittings | Stainless Adapters