Metal pipe and joints not tightening more than 50% of the way

[zfaiziahz]

I have a metal pipe and a tee join which needs to be tightened together. However, I just cannot get it to tighten any more than half way. The answer is probably very simple but I'm a newbie - what am I missing? Do I need a lubricant?

Here are the items I'm using:
> pipe: https://www.bunnings.com.au/brasshards-20-x-1200mm-galvanised-pipe_p0178265

> tee join: https://www.bunnings.com.au/brasshards-20mm-galvanised-tee_p0178305

P.s. This is for simple DIY project and no water/gas involved.

[MitchellMc · Accepted solution]

Welcome to the Bunnings Workshop community @zfaiziahz. It's marvellous to have you join us, and many thanks for your question about galvanised fittings.

The simple answer to your question is that galvanised fittings traditionally are not designed to thread in all the way. They have tapered threads, so the more you turn them, the tighter they get. Check out this recent discussion on the topic: Are these garden tap threads compatible? In some cases, you might only get three to four rotations before they lock; that's about 50% of the thread. Have a look online at some images of galvanised connections; you'll note that many do not thread the whole way in.

It's come to my attention that some suppliers have tighter tolerances than others. The fittings I have seen screw almost the whole way in before locking. In other cases, we've seen the threads lock much sooner. Regardless, the joint should seal adequately for their purpose and should still be structurally sound for other D.I.Y. projects. What are you making?

Please let me know if you have any questions.

Mitchell

[MikeTNZ]

Hi @zfaiziahz,

Please be aware that if a fitting does not screw straight on, it is misaligned and will only screw on for a 3/4 turn.

This is called cross-threading

The pipe and the fittings need to be "square" with each other.

[zfaiziahz]

Great to know, thanks mate!