Difference between MPT and NPT threads?

How can I tell by looking at it?
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poison snipped-for-privacy@yahoo.com wrote:

MPT (M = male) is a male NPT.
I once actually tried to explain to someone why some threads are called "male" and others "female". I failed completely. I won't try with you either.
Tim.
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On 07/27/06 12:40 pm snipped-for-privacy@trailing-edge.com wrote:

I remember that when I was perhaps 8 or 9 years old I heard the plumber who was working in our house refer to an "M and F" coupling. I asked what this stood for, and he told me that it was short for "Male and Female." When I asked why, he told me that I would understand when I was older.
Perce
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On Thu, 27 Jul 2006 13:41:19 -0400, "Percival P. Cassidy"

Do you understand yet?
I still dont understand because I have NEVER seen a pipe with either a penis or a vagina. Have you? <lol>
(I did see several pipes that had nipples though, so I instantly knew they were female) !!!!!!!!!!!! :)
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Hmmm. I'm a male, and I have nipples. What're you, some kind of evolutionary freak?
-Frank
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On Thu, 27 Jul 2006 14:59:54 -0700, Frank Warner

You DO?????? That's scarey...... Do men chase after you too???? I they do, get a bra :)
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Frank Warner ( snipped-for-privacy@verizonDOTnet.net) said...

Did anyone else just think of cats and Robert De Niro in Meet the Parents?
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You can't. They're the same.
"MPT" means "male pipe thread". "FPT" means "female pipe thread". "NPT" ("national pipe thread") is simply a generic term for that same pipe thread, male or female.
In other words, "MPT" and "male NPT" means the same thing.
Similarly, MIP (male iron pipe) == MPT and FIP (female iron pipe) == FPT.
http://en.wikipedia.org/wiki/National_pipe_thread
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Chris Lewis writes:

No, the "T" stands for "tapered", not "thread". As in NPS for straight threads, etc. The designations "NPT", NPS, etc., are part of the national standards (ANSI/ASME B1.20.1-1983 (R1992) etc).
"MPT" and "FPT" are bastardizations not in the standards. Likewise "FIP" and "MIP": common galvanized or black pipe is steel, not iron, and besides the thread standards have nothing to do with iron vs steel vs brass, etc.
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Just to confuse things. MPT is a subset of NPT. Because NPT can be MPT or FPT. So, they aren't totally interchangable. Not to be a PIA, cause a MPT would go nicely into a same size FPT, but can't guarantee that a MPT would go into a NPT, only if it's a FPT NPT. If it were a MPT NPT, that wouldn't work. So, if you have a NPT FPT on your SUV, you need a MPT NPT, or you'll be SOL. KWIM? Then, you'll need a BFG, or BFH.
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Stormin Mormon wrote:

I'm soooo confused.
Harry K
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replying to Chris Lewis, Mark McKelvy wrote:

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poison snipped-for-privacy@yahoo.com wrote:

And you can tell it from machine-screw thread by the couple-degree taper, not to mention the size. Guaranteed interference-fit, IOW.
J
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Threads that interfere are not necessarily interference-fit. Interference- fit threads are not tapered.
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poison snipped-for-privacy@yahoo.com wrote:

Okay thanks for your replies - but let me ask all of you this then (this is the crux of the question):
I am trying to replace an air pressure gauge on a piece of equipment (tire changer.) It has a male back mount. When I messure the diameter of the threads I get more than 1/2" Is this considered 1/2" Male - NPT ? (It's more like 5/8") Or do I have some odd thing that is going to cost me a fortune to replace. It doesn't appear to be tappered unless it is "very" gradually tappered.
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poison snipped-for-privacy@yahoo.com wrote:

Pipe thread are sized to be on the OD of common pipe which is sized by the Pipes nominal ID. Thus, 1/2" pipe is actually 0.840 inches in OD. 3/8" pipe is 0.675 OD. So it would seem that you're looking at a 3/8 pipe connection there if your 'more like 5/8"' observation is good. You can check the pitch: 3/8NPT threads have 18 threads per inch, 1/2NPT has 14.
Easiest thing to do is to check it against some fittings of known size: take it you local big box and screw some stuff from the plumbing aisle onto it and see what fits.

Almost certanly not: if it's just a pressure gauge, you can even adapt it to any old size and go from there.

The taper on NPT thread is about 1.75 degrees, about 3/4" in each foot, it's easy to miss.
John
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poison snipped-for-privacy@yahoo.com wrote:

Most gauges will be 1/4" NPT. I just checked my well gauge and it is 1/4" NPT and measures roughly 1/2" OD by holding a tape measure to it.
Harry K
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replying to Harry K, too much information dude wrote:

NPT is defined by ANSI/ASME standard B1.20.1.[3]
Pipe threads are different from machine-screw and bolt threads. Those are designated NC (national coarse) and NF (national fine.) The biggest difference is the taper on pipe threads.
The taper rate for all NPT threads is 1 in 16 (3⁄4 inch per foot or 62.5 millimeters per meter) measured by the change of diameter (of the pipe thread) over distance. The angle between the taper and the center axis of the pipe is tan−1(1⁄32) = 1.7899° = 1° 47′ 24″.
Nominal Pipe Size (NPS) is loosely related to the inside diameter of Schedule 40 pipe. Because of the pipe wall thickness, the actual diameter of the threads is larger than the NPS, considerably so for small NPS. Pipe of other schedules with a certain NPS has different wall thickness, but the same outside diameter and thread profile as Schedule 40, so the inside diameter of the pipe is therefore different from the NPS.
Thread form[edit]NPTE and NPS threads have a 60° included angle and have a Sellers thread form (flattened peaks and valleys).
NPTF[edit]A semi-compatible variant called National Pipe Taper Fuel (NPTF), also called Dryseal American National Standard Taper Pipe Thread, defined by ANSI B1.20.3, is designed to provide a more leak-free seal without the use of teflon tape or other sealant compound. NPTF threads are the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.
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