Threading NPS to NPT Threads

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Threading NPS to NPT Threads

Postby Smokehouse Shiner » Mon Jan 31, 2011 11:34 am

So I've googled and googled and the general consensus view is that your should not use taper threaded fittings on straight threaded fittings however: this is all for use in industrial and/or pressure type situations. So my question is does anyone have real world experience in using copper taper threaded fittings with NPS straight threaded fittings. Specifically I want to screw a 3" copper female threaded fitting onto a 3" NPS stainless fitting for a boiler to still head connection. So what do ya think? I know it won't fit properly or seal perfectly, but can I teflon tape the chit out of it or some flour paste around the connection and make it work for our low/no pressure applications? This is a very pricey fitting so I want some reassurance or discouragement that it's gonna be doable or not before I order. Thanks in advance!
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Re: Threading NPS to NPT Threads

Postby kenfyoozed » Mon Jan 31, 2011 11:49 am

A npt male should thread into a nps female. The last few threads on a npt should be the same size as nps. I just rethreaded a npt to nps. A few wraps of Teflon on the npt should help seal. I don't know if it would be strong enough to hold a column. Let us know how it works out.
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Re: Threading NPS to NPT Threads

Postby Smokehouse Shiner » Mon Jan 31, 2011 12:30 pm

Thaks Ken. I'm pretty sure it will work, just that 80 dollar fitting starin at me makes me nervous. I'd hate to fug up the threads and be stuck with it. I guess if noone chimes in that has done it I'll just bite the bullet and try it....
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Re: Threading NPS to NPT Threads

Postby kenfyoozed » Mon Jan 31, 2011 12:34 pm

You could buy cheaper fittings, say in the 1" range and try it out first. If it works there is should work when scaled up.
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Re: Threading NPS to NPT Threads

Postby Smokehouse Shiner » Mon Jan 31, 2011 12:44 pm

Good idea :idea:
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Re: Threading NPS to NPT Threads

Postby condensificator » Mon Jan 31, 2011 3:44 pm

i did my off the rack heater element into a 1" NPT 1/2 coupler. didn't even know that the element was NPS until a lot more threads about it popped up. threaded in no problem at all. has sealed up tight as a drum and been proven though a couple hundred gallons of wash and spirit runs. this of course was stainless to stainless, but i'd think that it might even be a better seat with the copper/stainless.

here's a link to one of the threads: http://homedistiller.org/forum/viewtopic.php?f=2&t=17828
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Re: Threading NPS to NPT Threads

Postby kenfyoozed » Mon Jan 31, 2011 3:56 pm

condensificator wrote:i did my off the rack heater element into a 1" NPT 1/2 coupler. didn't even know that the element was NPS until a lot more threads about it popped up. threaded in no problem at all. has sealed up tight as a drum and been proven though a couple hundred gallons of wash and spirit runs. this of course was stainless to stainless, but i'd think that it might even be a better seat with the copper/stainless.

here's a link to one of the threads: http://homedistiller.org/forum/viewtopic.php?f=2&t=17828


I hate you guys that this worked for. :ebiggrin: I had to buy a 40$ tap to make mine work, but mine were triclamps adapters, those 1/2 couplings must be made loose. But loose can be a good thing sometimes. :mrgreen:
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Re: Threading NPS to NPT Threads

Postby Smokehouse Shiner » Mon Jan 31, 2011 3:59 pm

Sweet thanks Condensificator. Thats what I needed- a shot of confidence. 8) I'm gonna give it a whirl. I'll let you know how it works.
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Re: Threading NPS to NPT Threads

Postby condensificator » Mon Jan 31, 2011 4:37 pm

kenfyoozed wrote:
I hate you guys that this worked for. :ebiggrin: I had to buy a 40$ tap to make mine work, but mine were triclamps adapters, those 1/2 couplings must be made loose. But loose can be a good thing sometimes. :mrgreen:

you could take a blank tri-clamp end cap ($4), drill a 1" hole in it, then weld one of the 1/2 couplers i got ($6) onto it. prolly cheaper than the tap or die route.

don't know...i would have never guessed that this would be an issue with hoe easy mine went together???
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Re: Threading NPS to NPT Threads

Postby Smokehouse Shiner » Sat Feb 26, 2011 9:17 pm

Update: It worked fine. 3" Female NPS threaded to 3" Male NPT. Several wraps of PTFE tape and threaded on hard hand tight. Haven't done a test run yet but it feels sealed to me. :D
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