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Old 12-09-2005, 11:59 AM
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What is the difference between npt and mnpt fittings.

I guess my question is...... will an 1/4" mnpt gauge screw in a fitting for 1/4" npt and seal.

Thanks
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Old 12-09-2005, 07:26 PM
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i bet one of those is a tapered fitting and the other is not
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Old 12-09-2005, 07:52 PM
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This may help some.....npt - national pipe thread...http://www.lesker.com/newweb/Vacuum_...late&init=skip
mnpt - male national pipe thread...http://www.hyvac.com/Products/Fittings/MNPT_fit.htm
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Old 12-10-2005, 03:22 AM
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NPT means National Pipe Taper. NPS stands for National Pipe Straight. It's not tapered and is used mostly in electrical fittings.

If you want to know more about threads and threading, I suggest a Machinery's Handbook, used in an older edition and cheap through online used book services like biblio.com. Lots more info on threads, screws and bolts (learn the difference between them) and gears, press fits, slip fits, metallurgy, etc, etc.
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Old 12-10-2005, 06:23 AM
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Quote:
Originally Posted by Neil Hochstedler

NPT means National Pipe Taper. NPS stands for National Pipe Straight. It's not tapered and is used mostly in electrical fittings.

If you want to know more about threads and threading, I suggest a Machinery's Handbook, used in an older edition and cheap through online used book services like biblio.com. Lots more info on threads, screws and bolts (learn the difference between them) and gears, press fits, slip fits, metallurgy, etc, etc.
EXCELLENT INFORMATION!
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Old 12-10-2005, 07:24 AM
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In answer to your original question, yes they will. However, a small amount of pipe dope or teflon tape or other sealer should be used on all threads that have npt in the thread description. Note that Teflon based sealers make tightening easier and as such make overtightening and deforming the thread easier also. With the teflon it is possible to tighten to the point that the female fitting will split. For those of you that feel the need to comment, try to keep it pg-13
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Old 12-14-2005, 08:00 PM
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Putting It Together

My personal recommendation would be to stay away from thread tape. That stuff is like RTV .... IE shows up in places it should not be. Permatex makes a high temp thread sealant in a squeeze tube or you can use old faithful .... aviation form-a-gasket. As one of the other members said ... Don't get it too tight as you can distort or break it.

Always keep in mind that pipe thread unions are designed to seal on the threads.

Straight thread connectors must have a seal such as a tapered seat in the female to mate with a beveled or flared end (check out a metal brake line) or else an o-ring (some fuel system connections) or copper washer (see the copper washer on brake calipers all the time).
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Old 12-15-2005, 06:27 AM
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I REALLY appreciate the information guys. Im rerouting my nitrous setup and I want large gauge so I don't make any mistakes on bottle pressure. I have been checking out the industrial gauges in ebay and just want to make sure what I put together will actually work ;-)

Thanks a TON guys!!
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