R134a Thread size?

I want to recharge the refrigerant in my auto air conditioner. I've assembled all the necessary tools except for one item. My vacuum pump is outfitted with a 3/4" female NPT fitting and the discharge tube from the gauge set is a R134a female fitting. I plan on machining an adapter to get the 2 fittings connected to each other.
But I can't figure out what the thread size is on the R134a. Please enlighten me!
Gary

gary wrote:
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1/2" Acme as I recall but I don't remember the pitch, sorry!
MikeB

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1/2" - 16 Acme according to this chart
http://www.epa.gov/ozone/snap/refrigerants/fittlist.html

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Don't reinvent the wheel by machining the fittings, it's silly to waste $100 to $200 of your time on a $5 part - you only do that when it's made out of pure Unobtanium... Go to any refrigeration supply house or search online.
They have in-stock adapters to go from NPT pipe thread to 1/4" SAE Flare (HVAC and Refrigeration charging hose fittings) 3/8" SAE Flare (manifold to vacuum pump hose connection) and 1/2" Acme Flare (R-134a Automotive Manifold hose fittings)
Your vacuum pump should have 1/4" SAE Flare and 3/8" SAE Flare fittings if it was made for refrigeration work - you connect the manifold hose with the 3/8 fitting, and can attach the micron vacuum gauge to the 1/4" to monitor your progress.
(If the system under vacuum has an extra service port, connect the vacuum gauge sensor directly to it. That way you can isolate the system with a ball valve and shut off the vacuum pump, and monitor the vacuum levels for leaks and/or trapped moisture still evaporating from the refrigeration oil.
If you are adapting an industrial vacuum pump, you'll have to bushing down from 3/4" NPT down to the threads needed for the adapter.
--<< Bruce >>--

gary writes:
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Beware you don't commit an EPA felony. Such adapters are not government approved.

On Sun, 14 Jun 2009 23:59:03 -0500, Richard J Kinch
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What the (heck) are you talking about? They don't have to be "government approved".
Unless they've made some serious changes since I took and passed the test, there are no approvals processes or "lists of approved machinery..." You just have to use procedures to reduce accidental or incidental release of CFC's and HCFC's as much as possible. And deliberate release is instant trouble.
A car using R-134a is running an HFC. No chlorine.
--<< Bruce >>--

Bruce L. Bergman writes:
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The EPA via the Clean Air Act regulates what fittings can be used with what refrigerants. Not the marketplace, not engineering standards, not the convenience or expedience of you or me or the OP. I don't agree with the despotism of the government, I'm just warning you. The law makes us all criminals, even for things like cutting metal. The tender mercies of the bureaucrats decide who is punished and who is given lenience.

On Tue, 16 Jun 2009 02:40:58 -0500, Richard J Kinch
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The service fittings permanently installed on the vehicle or stationary system, yes. If you do a conversion from R12 to R134a or another refrigerant you have to change the fittings to the proper style to avoid accidentally mixing refrigerants.
But not an adapter made so you can hook up your service manifold hoses to the car or refrigerator being serviced, or hook up the hose from your vacuum pump to your service manifold. They may be stupid MF's working for the government, but they ain't THAT stupid.
It's the mouth breathing politicians who wrote the impossible to follow laws the bureaucrats are trying to (selectively) enforce who *are* that stupid. Which is why politicians are like diapers - they need to be changed often, and for the same reasons.
--<< Bruce >>--

Bruce L. Bergman writes:
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The EPA holds that if certain fittings are required, then adapters to circumvent them are not permitted, since that defeats the very purpose of the fittings, namely to make impossible the mixing or confusing of refrigerants. While the utility of adapters is obvious, you're supposed to have a separate set of gages and hoses for each refrigerant. That's the governmental logic: intelligent economizing must give way to backstopping presumed stupidity.
As Uncle Al sez, environmentalism is expensive, shoddy, and deadly.

On Wednesday, June 17, 2009 at 3:16:09 AM UTC-4, Richard J Kinch wrote:
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So ..leave those fittings for R134a on your hoses because they are not adaptors, but a permanent conversion to make an obsolete tool usable. If it became necessary to permanently convert the tool to R12, do so at that time.

snipped-for-privacy@gmail.com wrote in
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So.... why are you responding to a SEVEN YEAR OLD post?

Bruce L. Bergman wrote:
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Want to bet!
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True, It is a shame that the Constitution was written by folks who felt that serving in government was such a PIA that nobody would WANT to do it. Term limits were not considered because of that.
I'd like to see term limits for ALL elected offices. Never going to happen though.

Steve W. wrote:
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The founders all had things to do, like managing a business. Government duties detracted from that.
I sure wish the people in Washington DC had other things to do. Idle hands truly are the devils workshop

RB wrote:
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Even the Devil has standards.

Michael A. Terrell wrote:
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Like the old joke about the testing lab that is switching from rats to lawyers:
1 - Lawyers are more numerous 2 - Nobody cares what you do to a lawyer 3 - There are some things even a rat won't do

RB wrote:
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They multiply exponentially.
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Except another lawyer, but they don't matter.
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Not when there are so many out of work law students who weren't smart enough to bribe their way past the bar.

Well we noticed this really old thread and see that it still gets lots of hits on Google. So if anyone is still looking...
Gary: "But I can't figure out what the thread size is on the R134a. Please enlighten me!"
I grabbed a bolt and checked if it screws in to the R134a in or out. It fits.
1/4" - 24
Meaning a 1/4" diameter bolt with 24 threads per inch (fine thread)
Someone should confirm this.... but does that help anyone?

On Friday, December 22, 2017 at 6:03:17 AM UTC-8, snipped-for-privacy@gmail.com wrote:
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thank you for posting the actual answer! I can't believe I had to read through 8 years of useless rants to find the answer. thanks again.

replying to melkie.au, fyiman wrote: I don't have an R134a fitting handy so I can't check it, but ...
The "normal" thread pitch for a standard 1/4" bolt is 20 threads per inch (TPI). The "normal" thread pitch for a */fine/* 1/4" bolt is 28 TPI, not 24.
So, if it was a fine-thread 1/4" bolt, it's 28 TPI. Otherwise, if not, perhaps you could check it with a thread guage.

replying to melkie.au, fyiman wrote: I don't have an R134a fitting handy so I can't check it, but ...
The "normal" thread pitch for a standard 1/4" bolt is 20 threads per inch (TPI). The "normal" thread pitch for a */fine/* 1/4" bolt is 28 TPI, not 24.
So, if it was a fine-thread 1/4" bolt, it's 28 TPI. Otherwise, if not, perhaps you could check it with a thread guage.