# Difference Between npt and upt Threadding ???



## jtice (Feb 21, 2004)

I was looking to see if I had a tap for 1/8" Loc-Line today, (1/8" upt-27) and noticed that mine said 1/8" npt-27.

What is the difference? What do the ywo mean?

Does this mean my npt tap wont work for the Loc-Line?

Thansk for the info.


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## tvodrd (Feb 21, 2004)

Pipe threads are tapered, and are designed to seal as they are tightened. The Japanese use what they call RPT, the British BSP, and the US has NPT (National Pipe Thread.)None of them seem to interchange very well. UPT is a new one on me. US 1/8" pipe is 27 tpi, and I suspect it will work for the Loc-Line. Best would be to do a test part first.

Larry


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## mahoney (Feb 22, 2004)

There is also an untapered pipe thread standard in America. Pitches and basic diameter are the same, but no taper. I've seen it on electrical conduit fittings, for example. Maybe that's what the UPT means but the standard abreviation is NPS. My Machinery's Handbook contains no reference to UPT.


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## MrAl (Feb 22, 2004)

Hello there,

There's UNC and UNF which are also straight. NPT is
tapered.
The main reason for the taper is to make a better
seal when tightened.

I've read that you can use a male tapered with a female
non-tapered if you put that teflon sealing tape on the
male end first, but you shouldnt use a male non-tapered
with a female tapered.
It was a long time ago -- but the main reason for any
possible problems was because of the way the two seal 
against leaks and didnt mean much as for the mechanical
strength. 

The straight fittings are said to be stronger than the
tapered fittings.

Take care,
Al


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## mut (Feb 22, 2004)

Here is about the best page I found to describe the different types.
http://www.jgbhose.com/base_pages/coupling_identification.asp
Hope this is helpfull.
mut


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## mut (Feb 22, 2004)

[ QUOTE ]
*jtice said:*
I was looking to see if I had a tap for 1/8" Loc-Line today, (1/8" upt-27) and noticed that mine said 1/8" npt-27.

What is the difference? What do the ywo mean?

Does this mean my npt tap wont work for the Loc-Line?

Thansk for the info. 

[/ QUOTE ]
I think maybe it is supposed to be tpi(threads per inch).
It matches up on specs for 1/8 inch npt.
mut


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## Bruceter (Feb 22, 2004)

I checked my Machinery's Handbook and found no reference to 
upt pipe threads. All of the Loc-Line that I have ever used had NPT threads, so your tap should work just fine.

Bruceter


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## jtice (Feb 22, 2004)

OK, thanks ALOT guys.

Maybe I just copied it down wrong or something.

Sounds like my tap will work fine though.

Heh, at least I just learned alot from all your great answers.
I wasnt aware of pipe threading for better seals. /ubbthreads/images/graemlins/smile.gif

Thanks.


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## McGizmo (Feb 22, 2004)

both NPS and NPT tapped holes will work with the Loc-Line. With NPS, the Loc-Line fitting will screw all the way down.


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## vendita (Feb 11, 2008)

HI Al,
I am a new user in this blog. working as a Grad Engineer in a O&G Industry. my issue is, I have to decide wheather to use NPT plug or UNF plug in order to permenanetly seal as well as contain pressure of about 2000 psi. hydraulic fluid (oil) is used inside the tool. 

this is because of the operator error caused while drilling a port of 1/2" -20UNF (tap dia.453" X deep.437") in a hollow tubular metallic tool. now we have to seal the hole with a blind plug and re-machine another port hole on another side.

bascially I have to analysis the sealing as wells the mechanical strength of the both type of threaded (NPT & UNF) plug to hold atleast of 2500 psi pressure. can u please able to help me in this regard.

ThX,
Ven




MrAl said:


> Hello there,
> 
> There's UNC and UNF which are also straight. NPT is
> tapered.
> ...


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## modamag (Feb 11, 2008)

John,

Loc-Line (US) are NPT. Sizes range from 1/8" NPT to 3/4" NPT.
Here's are some common ones that they normally carry.

1/8" x 27 NPT
1/4" x 18 NPT
3/8" x 18 NPT
1/2" x 14 NPT
3/4" x 14 NPT

Be aware of the clones! I got some stuff similar to the 1/4" Loc-Line which are not 1/4"x18 NPT. I think it must be metric or something.


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## Torque1st (Feb 11, 2008)

Jeez this was an old thread! :thumbsdow

Never mix straight threads and tapered threads, -very bad juju!!!


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