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Author Topic: PM research thread help  (Read 791 times)

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PM research thread help
« on: March 09, 2024, 09:43:52 am »
I have a Model #3 from PM.    I need to know what the standard thread type is for the steam inlet on this engine.     The website does not say what it is, nor
Does it allow you to select a specific thread. That being said, it has to be a standard size for the female steam inlet of them.

I know that pipes and fittings can be interchangeable but the engine steam inlet is NOT. It is one standard size.   I am guessing it is 1/4-40 UST? 

Anyone know? [ Guests cannot view attachments ]
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Re: PM research thread help
« Reply #1 on: March 09, 2024, 12:26:12 pm »
1/4 - 40 may well be a good guess, but the fact is that it may be an engine built from a castings kit by a home hobbyist who could have used almost any sized tap to produce your engine's steam inlet!

My own PMR #3 has a 3/16 - 40 thread at that location.
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Re: PM research thread help
« Reply #2 on: March 09, 2024, 04:06:08 pm »
Like Stoker said, it can be anything. The plans do recommend a thread size and perhaps that's what was used with a machined kit from PM. I think I still have the plans down at the shop, but 1/4 - 40 sounds too big. I'll see if i can find them.
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Re: PM research thread help
« Reply #3 on: March 10, 2024, 11:53:59 am »
My fully machined kit has 3/16 x 40 UST threads.
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D. E. Jones

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Re: PM research thread help
« Reply #4 on: March 10, 2024, 06:14:59 pm »
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Yup, 3/16x40.
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