What is causing my 1/4 NPT fittings to not fit together properly?

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In summary, the individual is trying to make a 1/4 npt fitting with two pieces of brass pipe. However, the tap and die do not seem to fit together properly and they are screwing in at an angle. The problem is suspected to be related to the "-5" on the die, but there is no clear explanation for what this means. It is possible that the die does not have the same number of threads per inch as the tap.
  • #1
axemaster
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Ok, so here's a weird problem. I am trying to make a 1/4 npt fitting with two pieces of brass pipe.

The tap says:

Vermont
1/4 NPT 18
HSGG M21

The die says:

1/4 NPT
Baystate -5

So I threaded the pieces of pipe, expecting them to fit together nicely... and they didn't - far from it. I found that they were screwing in at an angle, and stopping after a short distance.

Needless to say I'm mystified by this. I've tried threading several pieces, being careful to make nice straight threads, and still this problem remains. I suspect it must have something to do with that "-5" on the die, but I haven't been able to find any references explaining what it means.

Please help!
 
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  • #2
I would imagine because it isn't a 1/4 NPT 18 die. I don't know what "baystate -5" means and I don't think it has to do with the die size (manufacturer maybe?). Regardless, your die probably just doesn't have 18 threads per inch like the tap does.
 
  • #3

Related to What is causing my 1/4 NPT fittings to not fit together properly?

1. Why are my Npt sizes not fitting properly?

There could be several reasons why your Npt sizes are not fitting properly. One common reason is that there could be a mismatch between the male and female threads. Another reason could be that the threads are damaged or worn out due to repeated use. Additionally, it is possible that the incorrect Npt size was purchased.

2. How can I determine the correct Npt size for my project?

The best way to determine the correct Npt size for your project is to measure the diameter of the male and female threads using a caliper or thread gauge. You can then compare these measurements to a sizing chart or consult a professional to ensure accuracy.

3. Can I use Teflon tape to help my Npt sizes fit?

While Teflon tape can help create a tighter seal, it should not be used as a solution for ill-fitting Npt sizes. It is important to properly measure and select the correct size for your project to ensure a secure and leak-free connection.

4. What should I do if I accidentally cross-thread my Npt sizes?

If you accidentally cross-thread your Npt sizes, it is important to stop immediately and try to realign the threads. Attempting to force the connection can damage the threads and make it even more difficult to achieve a proper fit. If the threads are too damaged, it may be necessary to replace the fittings.

5. Are there different types of Npt sizes?

Yes, there are several different types of Npt sizes, including tapered and straight threads. It is important to understand the differences between them and select the appropriate type for your project. Additionally, Npt sizes are available in various materials, such as brass, stainless steel, and plastic, so it is important to choose the right material for your specific application.

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