Air Hose Fitting--Plastic OK?

npalen · Dec 20, 2017

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 · Dec 20, 2017

npalen said:
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 · Dec 20, 2017

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 · Dec 20, 2017

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 · Dec 21, 2017

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 · Dec 21, 2017

npalen said:
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 · Dec 21, 2017

s219 said:
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?