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Author Topic: Need help with brass nipple sizing  (Read 1313 times)
Julian
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« on: May 09, 2013, 12:10:20 am »

So I am connecting up a series of pipes.  The pipes that I found that have threading on the outside are called nipples.  The problem comes in making everything fit together.  For example, I have a 1/2 inch diameter brass nipple.  This tells me I should need a 1/2 inch coupler or reducer.  The problem is that it only screws on for a few threads then it stops.  I want things to be flush with no threads exposed.  I looked at the nipple and I think I found the problem.  Each thread is slightly higher than the next so eventually the threads are too big to fit the coupler. 

I tried going up in sizes.  A 5/8 inch flute cap fits on it, but a 5/8 inch coupler is too big.  So, is there any other pipe with thread on the outside I could use beside a nipple?  Is there anything I can do to make things flush with no thread exposed? 
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Narsil
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« Reply #1 on: May 09, 2013, 12:49:05 am »


The reason for that is that pipe threads are tapered which is there to ensure a tight seal with mechanical thread only. This almost impossible to achieve with parallel threads. Not all pipe standards use tapered threads but you don;t always haev the choice for a given connector size.

If you want a flush fit with standard parts you will need either push fit or soldered connectors. If the strength of the joints insn;t vritical then  the simple solution is just to file the threads down until they fit and epoxy them together.
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RJBowman
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« Reply #2 on: May 09, 2013, 01:10:27 am »

I read the title of this discussion as "Need help with brass nipple ring sizing".
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Will Howard
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« Reply #3 on: May 09, 2013, 01:13:38 am »

I read the title of this discussion as "Need help with brass nipple ring sizing".

Shame on you!
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Julian
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« Reply #4 on: May 09, 2013, 01:25:30 am »

I don't have any way to solder pipes properly, so I guess that is not an option.   

Any recommendations on what to use to file the threads down? 
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Narsil
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« Reply #5 on: May 09, 2013, 01:36:19 am »

at the risk of being facetious a file would be the best thing.
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Maets
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« Reply #6 on: May 09, 2013, 01:38:44 am »

You can back fill the exposed threads with solder or epoxy or something else.  Assemble everything, then fill in the threads and smooth.
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grimnir
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« Reply #7 on: May 09, 2013, 02:10:43 am »

You really need tapered thread fittings to match. For example 2 common thread gauges are BSPT and NPT. You also have coarse and fine threads. If you really want to use the fittings you have get a parallel thread die to match the fittings and rethread the nipples with that.
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Julian
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« Reply #8 on: May 09, 2013, 05:22:51 am »

I am fine with buying new fittings, I am just not sure what ones to get.  The store doesn't list threading types on any of the packages.  All I really need is a 1/2 inch diameter pipe connected to a 1/2 inch to 1/4 inch reducer.  The reducer is then connected to a 1/4 inch pipe.  If there are ones where the threading matches and goes in smoothly, I would be happy to purchase them. 
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von Corax
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« Reply #9 on: May 09, 2013, 06:37:01 am »

Since you're in the US, the pipes are almost certain to be NPT taper-threaded. I'm wondering, though, if there's a reason you're using threaded-joint pipe instead of solder-joint (which can be epoxied if it's just for looks) pipe?
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Julian
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« Reply #10 on: May 09, 2013, 05:21:29 pm »

I probably don't have to use threaded pipe.  In all honesty I never thought much about pipe other than with threads I can hold everything together.  The only issue I see about the threads is that I will be putting batteries in part of the contraption.  I will need some way to open it and replace the batteries as needed.  Having an end I can screw off and on helps with that, but I am sure there is another way to give me access to the batteries.  I just need to think about it. 
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oldskoolpunk
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« Reply #11 on: May 10, 2013, 08:10:04 am »

Tapered threads are intended to be tightened only once. They get a tight seal by deforming the metal slightly.  So if it has to be unscrewed to change batteries, a tapered thread joint will be troublesome.
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Julian
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« Reply #12 on: May 10, 2013, 03:35:42 pm »

I think what I am going to do is replace the brass nipples with copper pipe and then glue it all together.  For the battery, I am going to add a FIP to MIP coupler to the copper pipe in place of the cap I am using.  Then I will add the end cap to the coupler.  This should allow me to replace the batteries and avoid the threads showing. 
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Steam Titan
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« Reply #13 on: May 14, 2013, 08:13:26 pm »

I read the title of this discussion as "Need help with brass nipple ring sizing".

oh good it wasn't just me
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