Cutting 3/8th NPT??

[Adoom]

Does anyone in Wellington/hutt have the means to cut a female 3/8th NPT thread?
I have an alloy tank that I want to use some brass fittings on.
It has 10mm thick alloy bosses welded on, but I have NFI how to cut the thread for the brass fittings.

[evil_si]

I have a tap to suit, but im in tauranga
If you get stuck i could send it down

[Grrrrrrr!]

http://tradetools.co.nz/products/6576300 but at that price you'd want to use it more than once..

Would just try your local engineer, chances they already have the tap so if you drill the hole to the right size they should tap it for a tenner or so.

[Adoom]

I have a tap to suit, but im in tauranga
If you get stuck i could send it down

Cheers, I'll try find someone local first.

[Adoom]

http://tradetools.co.nz/products/6576300 but at that price you'd want to use it more than once..

Would just try your local engineer, chances they already have the tap so if you drill the hole to the right size they should tap it for a tenner or so.

Yeh, they are pretty dear to buy. I only need to use it 3 times.

[Stott69]

Will ask what size we have at work tomorrow

[Adoom]

I'm confused as to WTF this tapered thread is.
Using my vernier....
If this is an imperial thread, the TPI is 20.
If this is a metric thread, the pitch is 1.3
The distance from thread peak to thread peak is 1.05mm
The big end of the taper is 16.75mm the small end is 16.15mm. Those two measurements are 9.5mm apart.

3/8th NPT is 18 TPI
3/8th BSP is 19 TPI

WTF is this thread?

[Lloyd]

Would 1.05mm between threads make it 24 TPI anyway? Something doesn't add up in the measurements

[Mr Revhead]

Anything here:
http://www.britishfasteners.com/threads/bsf.html

Also measuring pitch with verniers is hard to get accurate

But being a brass fitting I'd have thought it would be NPT or BSP with the rare possibility of metric. Where did you get them from?

[Burning Angel]

you measurements for taper are close enough to 3/4" per foot which both npt and bspt are.

as Lloyd pointed out 1.05mm pitch is 24 tpi

the main difference between npt and bsp is the tpi and the included angle of the threadform- npt is 60° and bsp is 55°

also the maj dia of npt is .675"(17.145mm) vs bsp at .656"(16.662mm)

[Adoom]

Would 1.05mm between threads make it 24 TPI anyway? Something doesn't add up in the measurements

I know, right..

The google images search I did said to get the TPI count the threads in 1/4 inch and multiply by 4(it's shorter than 1 inch). So I set the vernier to 1/4" and there were exactly 5 threads.
So TPI = 20.

But if I measured as exactly as I can from peak to peak on the threads, I got 1.05mm... which doesn't add up.

Buuuuut, long story short. I went to TWIGGS at lunch time and I'm like "Dude, WTF is this thread?!" And he was like "SHAZAM!, BSPT".
Well, that's how I remember it, it was almost two hours ago!

[Mr Revhead]

I do hope he actually said shazam

[Adoom]

I do hope he actually said shazam

Yep, I remember it clearly, the sky was black and full of fire and lightning. Bunnies and rainbows were streaming out of the store, fleeing for their lives ahead of the Godzilla monster. So what do these pills do? Where am I?

[85AW20v]

I do hope he actually said shazam

Yep, I remember it clearly, the sky was black and full of fire and lightning. Bunnies and rainbows were streaming out of the store, fleeing for their lives ahead of the Godzilla monster. So what do these pills do? Where am I?

And where do we buy them?