1 Inch BSP Outlet Fitting

[Stevieboy]

I now understand what you are saying.

The peaks of the male thread will always remain parallel to the valleys of the female BSP thread.

What changes in a tapered thread is that the valleys of the thread get shallower. You can clearly see that if you look at the thread. You can screw a male parallel thread all the way home in a female thread. Use the same female thread with a tapered male thread and the male will start to tighten up the further you screw it in. You won't be able to screw it in as far you did with the parallel thread male fitting.

In the original design the concept was that a seal or gasket would be located at the end of the female thread on BSPP to seal the 2 joins. Tapered thread would seal the threads with the aid of a sealant to prevent leakage due to manufacturing imperfections.

When using a fitting into a water tank the correct fitting to use would be a tapered thread. But in the hands of an unskilled person they could overtighten the male fitting and crack the brass socket in the tank outlet. So the best advice to cover all bases is to only use BSPP fittings and seal the threads with PTFE tape or some other liquid sealer. Even winding too many wraps of PTFE tape can cause the female socket to crack if overtighened by someone you doesn't have the 'feel' to know how far to tighten it.

You are still not getting it. Not part of the thread on the tapered fitting is bigger than on a parallel fitting. So it will go in the same as a parallel because it’s not bigger. The physical o/d of a tapered male is slightly smaller or let’s call it the same as a parallel. It would not crack. 

 

[doug atkinson]

I don’t want to get into an argument about this. But with a BSP thread not BSPP if I screw in a BSP male thread the whole thread goes in no problem. With a BSPT thread it will not all go in without force. This is even without any ptf tape. You can tighten it with a spanner. The metal used on that tank I think is aluminium. It is not a thick thread but thin so there will be an issue later on with BSPT. In my past experience I used BSPT metal into BSP female plastic and I learnt the hard lesson in crack, hairline. It is better to be safe than sorry in the long run.

 

[Stevieboy]