# Left Hand Thread Pipe Taps???????



## JimDawson (Aug 31, 2015)

My neighbor picked up a few boxes of stuff at an estate sale.  One of the boxes has a few left hand thread pipe taps from about 1/8 to 1/2 NPT.  These are standard NPT taper.  In 50 years of being around this stuff I have never seen a left hand thread pipe tap before.

Anybody have an idea what these might be used for?
.

.


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## Ulma Doctor (Aug 31, 2015)

i didn't know they made left handed NPT either, 
might be Nuclear/NASA type stuff


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## Ed ke6bnl (Aug 31, 2015)

when I worked installing A/C central air over 35 years ago we would use a left right fitting for gas lines in the attic where you could not use unions. it would join to pieces one left hand the other right.


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## Tony Wells (Aug 31, 2015)

Fuel gases often use LH threads to keep from getting mixed in with air or oxidzer gases. I think you will find smaller gas regulators with LHT ports.


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## JimDawson (Aug 31, 2015)

I just did a web search for them, looks like they are commonly available.  Learn something new every day.


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## RJSakowski (Aug 31, 2015)

I have an ancient steam autoclave.  The stand for it is made from 12 sections of threaded 3/4" pipe, like so:
	

		
			
		

		
	



The only way this could be assembled would be if both left and right hand pipe threads were used.  Idon'tknow if they are tapered or straight pipe threads though.

Bob


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## GK1918 (Aug 31, 2015)

Very common with gas lamps back in the day so there would not be an ugly unions visible. 
My mother in laws house still has the gas  pipes no unions.  I too have those, but the rare
thing is finding left dies.   .....


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## Eddyde (Aug 31, 2015)

Ed ke6bnl said:


> when I worked installing A/C central air over 35 years ago we would use a left right fitting for gas lines in the attic where you could not use unions. it would join to pieces one left hand the other right.


Here in New York City it is illegal to use unions anywhere in a gas system so left-right connections are common. They are usually sold as a set consisting of a 6" nipple and a coupling each with one end left hand treaded.


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## RJSakowski (Aug 31, 2015)

GK1918 said:


> ..... but the rare
> thing is finding left dies.   .....


That's why we have lathes.


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## Bill Gruby (Aug 31, 2015)

You can take this as Gospel, if there is a Tap, there is a Die to match.

 "Billy G"


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## JimDawson (Aug 31, 2015)

Bill Gruby said:


> You can take this as Gospel, if there is a Tap, there is a Die to match.
> 
> "Billy G"




Yup, it seems that most to the major vendors have them and you can buy right/left pipe nipples.  You would think that as long as I have been around industry that I would have run into them before.  We just keep learning.


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## KBeitz (Jul 1, 2018)

Steam manifolds was made from cast iron. 10 pipes each.
One end was left hand threads.


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