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Old 05-17-2017, 09:53 PM   #1
John V
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Tire machine weirdness

I have a tire machine. It is awesome. Maybe the best tool I've ever purchased.

It's about 8 years old and was heavily used, and I got it really cheap because it needed some work. Nothing major - some leaking air connections. Tire machines are largely pneumatic. Air leaks are annoying when you have an undersized compressor like I do.

So I'm gradually figuring out what the various fittings are and replacing them. The fitting in this pic (on the top) is at the top of the pressure tank and is what feeds air to the whole machine, essentially.



I called the company that sells parts and they sent me the one on the bottom, saying it's an upgrade to the original part. It doesn't fit. They claim it will. Looks like it should, but it doesn't.

I compare it to the one off my machine, which is a tapered pipe thread of some sort. By eye it looks to be 1/4" NPT. The fitting that the parts company sold me clearly has straight threads. Okay, simple mistake, so I return those fittings and go to Amazon. Amazon sells a 1/4" NPT to 8mm tube elbow. My machine has 8mm tube and this looks like a 1/4" NPT fitting. It measures a little more than 0.5" on my calipers and has about 18 threads per inch (hard to measure on a tapered thread). I order that fitting.

It doesn't fit. The diameter is too large. I measure things more carefully with a micrometer. 1/4" NPT should have a major diameter of 0.540". This fitting is 0.512-ish. I carefully measure the threads per inch. I keep coming up with 19 threads per inch. Hm. I do some searching. These dimensions match a 1/4"-19 BRITISH pipe thread.

Fucking BRITISH. On a machine made in the USA. That uses 8mm tubing.
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Old 05-17-2017, 11:00 PM   #2
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Old 05-18-2017, 12:19 AM   #3
lip277
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Sounds like my old S-10 truck.

The engine was all metric. The body SAE. Drove my f*&^% nuts.
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Old 05-18-2017, 12:25 AM   #4
rumatt
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Chevy S10?
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Old 05-18-2017, 05:21 AM   #5
John V
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Co-mingling metric and SAE doesn't bother me. Pipe threads are almost universally inch units.
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Old 05-18-2017, 08:28 AM   #6
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When ever I need to replace an odd ball air fitting, Graingers has always been my friend

Edit: Graingers and I were great friends when I owned, and was converting my Volvo 780 to RV use.
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Old 05-18-2017, 08:38 AM   #7
Josh (PA)
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can you just tap the mating hole to 1/4 NPT? Might be easier than chasing fittings all the time.

Edit, nevermind didn't pay attention to the 18 vs 19 tpi. That's stupid.
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Old 05-18-2017, 11:25 AM   #8
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Can you still easily source the British part?

I'm still very jealous that you have a tire changer. It will be one of my first purchases one day when I have a garage.
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Old 05-18-2017, 01:01 PM   #9
John V
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Amazon had one in stock for seven bucks. So no big deal. It's just a bizarre fitting. Makes me wonder if the regulator on top of the air tank is not factory.

I typically go to McMaster or Grainger for this kind of stuff, but honestly Amazon is easier to search and I get free shipping, so...
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Old 05-18-2017, 01:22 PM   #10
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Quote:
Originally Posted by John V View Post
I typically go to McMaster or Grainger for this kind of stuff, but honestly Amazon is easier to search and I get free shipping, so...
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