NPT threads

[homers brew]

Hi all,

I need to secure the back of the PT100 inside my vessel with a backnut. Where do you lot get yours?

It looks like 1/4" NPT.

Or would I be able to bodge a BSP fitting?

(Note - It's not the same as the 1/2" fitting which I have searched and read are bodgable, as these have the same TPI - whereas the 1/4" have 19 and 18 TPI).

Thanks all.

 

[mickeyt69]

You could maybe run a 1/4 BSP die nut down it to cut a new thread but idealy you shoud source an npt fitting personaly i dont like bodging threadsgoes against my mechanical ethos.

just had a look for a site with NPT fittings too many out there argh!! are you after a flanged nut?

 

[homers brew]

You could maybe run a 1/4 BSP die nut down it to cut a new thread but idealy you shoud source an npt fitting personaly i dont like bodging threadsgoes against my mechanical ethos.

just had a look for a site with NPT fittings too many out there argh!! are you after a flanged nut?

I'll be buggered if I can find any of them......maybe it's because I don't know where i'm looking.....I don't suppose you could provide a link to somewhere where I can order online.

No just a backnut to secure the pt100 into the tank wall.

 

[prolix]

I bought a 1/4" npt tap and cut threads on brassware from bnq worked a treat. They are not cheap at ~£15 +p&p

 

[mickeyt69]

jees shame im not still at work i could have 'borrowed' one and sent it come to think of it i could have just got the nut for you. ill look for a link

 

[mickeyt69]

http://www.intlcordsets.com/components/misc_locking_nuts.php are these what you are after? top one on there

 

[homers brew]

http://www.intlcordsets.com/components/misc_locking_nuts.php are these what you are after? top one on there

Thanks Mickey.

Oh, did I fail to mention stainless.....and it if didn't have to be shipped from the states would be a bonus. I expect they are easily obtained over there.

I have contacted a pipe fittings supplier over here, but will have to wait until tomorrow at least for an answer.

 

[mickeyt69]

is it urgent ? if not i might be able to ahem lay my hands on one if not swagelok make pretty much anything

 

[mickeyt69]

sorry didnt realise it was states based but you should be able to get one over here they are a common thread in industry here

 

[homers brew]

The reply from a pipe specialist...

"Hi, NPT is a tapered thread so a locknut is not available.
Regards
xxx"

Maybe I am asking the wrong question....locknuts/backnuts/muttsnuts...???

Have another lead I am following now anyway.

 

[lukesharpe]

Did you find the right fitting for the PT100? I'm in the same boat need one for mine. Any luck?

Ollie

 

[homers brew]

Did you find the right fitting for the PT100? I'm in the same boat need one for mine. Any luck?

Ollie

I found a vacuum part pipe end end cap fitting with an NPT thread and bought it although it needed the centre drilling out of it....this came but at tthe same time since i had an order in with BES at the same time added a 1/4" bsp backnut to it. The Bsp backnut seems to fit the thread although I haven't fitted it yet so can't say for definate yet if it will hold. It did screw right up the thread of the PT100 which I didn't expect it to, the two threads having different TPIs.

Hope this helps, if you like I could post you a backnut to try if you like if it saves you taking out another order, I don't need them all in the immediate future.

 

I took my probe to the local precision engineers, where they promptly told me it was 1/4" BSP/Gas.
The nut they made fits perfectly!

 

[homers brew]

I took my probe to the local precision engineers, where they promptly told me it was 1/4" BSP/Gas.
The nut they made fits perfectly!

Yes, the confusing part though is when they were bought it stated that.they were npt, although, as you say a bsp nut fits them. I may get the vernier on it at the weekend.

 

I may get the vernier on it at the weekend.

I'll be very interested in your conclusions :thumb:

 

[homers brew]

Right then....these are the PT100 sensors from virtual village.

I have measured the thread with a vernier and this produced a measurement of 7.96mm over 6 turns of the thread. Unfortunately this is all by eye so not ideal but I think it may just about give an accurate enough reading without using a thread guage or similar.

So that's 7.96mm/6 threads = 1.326mm/thread
Convert to old money 1.326/25.4 = 0.05223"/thread
Take the reciprical 1/0.05223 = 19.145 tpi

However, a standard 1/4" bsp backnut goes right up the thread (disclaimer - on the one I have).

Conclusion...god knows but a bsp backnut fits the ones I have.

 

So are you going to stick with 1/4" BSP?
I have :thumb:

 

[homers brew]

So are you going to stick with 1/4" BSP?
I have :thumb:

Yep. Npt are hard to source. Just thought I'd put it down so no one else tries to source the quoted npt threads when they don't have to it seems. That is if they have the same sensor as me.

 

[A T]

I have 2 or 3 of these nuts, i'll be happy to post them on to whoever wants them later in the week when i get a chance, pm me. Not sure if i have 2 or 3 so first come first serve.