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Pipe nipple or Threaded nipple?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Pipe nipple or Threaded nipple?

Unread postAuthor: LikimysCrotchus5 » Fri Jan 04, 2008 9:12 pm

I know this may seem to be a wasteful topic but its concerning me.

Also, what i mean by a coupling is a nipple that is threaded but in the center it isnt threaded therefore having 2 seperate threaded parts on one piece. by a nipple i mean that the whole thing is threaded.

I have a propane meter built and with this meter i have a 1/4 inch pipe nipple that goes to the chamber. But in this pipe nipple there is a space where there are no threads. I found this to be useful because i can tighten the pipe nipple in that area without destroying the threads.

EDIT: Well for you, DYI, and for Me, here is simpler, and correct terminology with pictures.

Image
This is a pipe nipple. This is what i have on my propane meter right now. This is the part that connects to the chamber. To tighten this, simply use a wrench and clamp in the middle and turn clockwise.


Image
This is a threaded nipple. It is what i would possibly consider putting on my propane meter so that it connects to the chamber. This gives the chamber and the threaded nipple less stress because it is shorter than a pipe nipple and the meter can be put closer to the chamber compared to a pipe nipple. But how would i tighten this without ruining the threads?
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Last edited by LikimysCrotchus5 on Fri Jan 04, 2008 9:49 pm, edited 3 times in total.
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Unread postAuthor: DYI » Fri Jan 04, 2008 9:21 pm

That is the most confusing thing I've read all day...

To start things off, a coupling is a female threaded fitting with two ports pointing at 180 degrees from each other.

A nipple is a short, threaded piece of pipe, usually less than 18" long.

A close nipple is a nipple so short that the threads meet in the middle
(note: a system that contains close nipples will invariably leak in the exact spot where fixing the leak requires destroying and replacing the close nipple)

Would you kindly reword that post using intelligible terminology so that we can offer some assistance?
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Unread postAuthor: daberno123 » Fri Jan 04, 2008 9:40 pm

I have no idea what you just said but if you're building a propane meter why would you worry about destroying the threads? You aren't going to need to take it apart are you?
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Unread postAuthor: DYI » Fri Jan 04, 2008 9:48 pm

Ok, now that we have the terminology cleaned up: to tighten close nipples, you have to grip the fittings on both sides of them, and turn in opposite directions. Of course, your problem is threading it into the side of a PVC pipe, which is a far softer material than the steel or brass that the nipple is likely made of.

You have no way of tightening the close nipple into the meter elbow before tightening it into the chamber wall, and since the PVC is soft, it will crack before the nipple achieves a decent seal with the steel elbow.

A hex nipple is about the same length as an equivalently sized close nipple ( as well as about 5x the cost :roll: ), and is conveniently provided with a protruding hex for a wrench to grip. As long as you stick with small sizes, hex nipples are probably the way to go, if I'm understanding the purpose of this post.
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Unread postAuthor: LikimysCrotchus5 » Fri Jan 04, 2008 9:50 pm

Ok thank you, sorry to confuse you.
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Unread postAuthor: Novacastrian » Fri Jan 04, 2008 9:58 pm

If you get two nuts that fit the thread of the nipple you can easily tighten it by screwing on the first nut, followed by the second, then using the correct size wrench hold the bottom nut still and tighten the second nut on top. Use the top nut to screw the fitting into place. To get the nuts off repeat in opposite order.

That clear as mud?
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Unread postAuthor: DYI » Fri Jan 04, 2008 10:14 pm

That clear as mud?

Significantly less so, actually :scratch:
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Unread postAuthor: Novacastrian » Fri Jan 04, 2008 10:37 pm

You use the same technique one uses to extract a head stud in an engine, except in reverse, since he wants to screw the "nipple" in and not ruin the thread. Another way is to put a hacksaw cut through one wall of a nut and use vice grips to tighten the nut on the thread after screwing it on,but that can crush your nipple, ouch!

Here is a pic to filter out the silt.
Image
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Unread postAuthor: jimmy101 » Sat Jan 05, 2008 12:39 pm

Isn't there another significant difference between the various "nipples"?

In the OP, the first photo looks like the nipple is NPT (normal pipe thread), doesn't that mean it tapers? Any nipple you picked up from the hardare store's steel pipe section is probably NPT.

The second photo doesn't look like there is any taper and it looks like a standard thread. The second photo looks like the nipple used in light fixtures which is a straight thread.

You can use a pair of nuts as jam-nuts on the straight threaded component like Nova posted. I don't think that would work on an NPT nipple with full length threads (not sure those even exist).
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Unread postAuthor: mark.f » Sat Jan 05, 2008 12:57 pm

I agree, that second picture looks like a nipple you run wires through, not a pipe nipple.

A pipe nipple where the threads meet in the middle is a "fully threaded" close nipple. Like DYI already said, you just coat in sealant, thread a little into one fitting, a little into the other, and then grip the fittings with wrenches and tighten. For PVC, like DYI said, this won't work.

You could try a Dremel head for sanding wheels, (a rubber drum that expands when tightened), to insert into the nipple while threaded by hand into the meter elbow, and then tighten with a pair of pliers on the dremel head. Then, thread into the plastic. I don't know the exact OD range of those drums, though, so this may or may not work.

If that doesn't work, just grab the nipple somewhere in the middle with vice grips and tighten. Very seldom do the fittings overlap the entire nipple, so you'll probably be good.
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Unread postAuthor: LikimysCrotchus5 » Sat Jan 05, 2008 1:36 pm

I dont know i put this through google images and this is what i got. But the pictures are only to show the difference between one thats fully threaded and another that is not fully threaded. But if you want to find imperfections in my posting then thats fine with me, as long as i got the point across :D

But that idea seems very feasable Nova, so i might try that. But can i still use this pipe nipple for my meter? (this is the piece that will go into the cannon).

If so, then what should i use?

I didnt quite understand your post mark, as i dont know alot about hardware, but i get the general idea of what you are saying.
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Unread postAuthor: frankrede » Sat Jan 05, 2008 2:40 pm

LikimysCrotchus5 wrote:I dont know i put this through google images and this is what i got..

Thats your problem
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Unread postAuthor: LikimysCrotchus5 » Sat Jan 05, 2008 2:46 pm

I dont consider it a problem, i just got my point across, so there is no problem, what i think.
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