Humble Pie
One McMaster Carr 1/4 NPT Male to Male Fitting (51205K132) +
One 1/4 NPT oil-rig designed HPA valve that took doing to get.
=
Completely destroyed threads.
So all in all, this experiment cost me about as much as my Condor, and I understand that “you have to lose some” BUT, I’d at least like to learn a lesson and I was hoping you guys might help me out on that part.
Now, you guys know I’m as ignorant as they come when it comes to mechanical awesomeness, but I assumed that NPT 1/4 from McMaster and NPT1/4 from a large US valve manufacturing co would be completely compatible.
I was only able to screw the fitting into said valve about 1/2 a turn before I met hard resistance. I said fine, lets leave it “hand tight” and see what leaks. At <600 psi, this thing was already leaking so I bring out the 8″ baby wrench and proceed to tighten another full turn.
Still leaks, so I pull it out and wrap in telfon tape for another go.
Still leaks, so go another half turn or so before I am lifting up the bench my vice is attached to with the force I’m using.
Still leaks, so I undo the thing and find this:
The motherfucking HORROR. I just did that, me, to myself, FUCK.
The only time I’ve ever seen anything like this happen before is when one tries to force a piece of a particular threading down the throat of a differently threaded orifice.
Now, I probably should have known at a certain “gut” ft/lb of torque that something was off, but I’m a noob, this is the price we pay to play.
My question is, as I clearly have been kept up late by this fiasco, is what the hell happened?
The valve input and outputs are threaded down at least 10mm and the mcmaster m2m has 12+mm of threading, I cannot see how two properly threaded parts jamming at <3mm makes any sense, especially with it leaking as such. As far as I understood it, the taper in NPT is what made the magic happen, but there was no magic here tonight.
What the hell do you guys think?
(nothing to see here, still leaking like a mother.)
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Viewing 10 replies - 1 through 10 (of 10 total)
Yes, they are compatible, look at your valve. Use a crescent wrench to turn the tap, just keep it straight.
Lol, thanks.
Now a question of methodology:
This:
With This:
Or This?
Also, is this true or false? “NPTF threads are compatible with NPT threads”
DAMNNNN ITTTT
It could be possible, the threads at the bottom of the valve look OK. If tapped correctly it will get the fitting into the untouched threads. It is a lot of pressure though, use caution or let your wife try it first.
Lol. I learn my making mistakes, story of my life. It’s good to be able to share my fiascos here though, thanks for reading.
Do you think that if I get a 1/4 NPT tap I might be able to bring these threads back to half-useable?
As far as the small fortune worth of NPTF fittings…damn.
Ugh….
Sorry to see that.
Wow fairlyinc, I am honored. Never thought I’d meet Rube Goldberg in my lifetime.
walt
GAH. I’m an imbecile.
The goal is to get enough flow from the tank to the gutted valve.
There’s a pressure sensor in the tank that talks to my mangled valves depending on tank pressure, it will lengthen or shorten the amount of time the valves are open, down to about 61hz accuracy.
The trick being that for any given projectile weight, as homogenous as possible an amount of force is applied, giving you the flattest string you’ll ever see coming out of an air force gun; thats the idea at least.
The devil is in the details, and god damn it if I didn’t just gimp myself with NPT vs NPTF.
PS That is quite a contraption you got going there, what is the goal?
Below is the description from McMaster Carr, NPTF is not the same as NPT
Shape Nipple
Nipple Type Hex Nipple
Pipe to Pipe Connection NPTF x NPTF
System of Measurement Inch
Pipe Size 1/4″
Material Type 316 Stainless Steel
Maximum Pressure @ 72° F 7200 psi
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Retapping worked *much* better than I expected, my babies are back.
Thanks for the advice.