How to seal the threads?

[wvkeith]

My PCP tube is steel and the plug that screws into it is brass. The plug has an o-ring on it but it keeps blowing out when I pressurize the tube. Is there anything I should seal the threads on the plug with?

[tat2dman]

Is it a Jack Haley tube?

[Avox]

As a general rule mixing brass and steel threads does not work very well. The pitch on the threads is very different and the brass threads will deform when tightened to steel threads.

With an o-ring the seal should be made with the o-ring between the mating materials. What you might be seeing is the result of too soft of an o-ring or inadequate compression of the o-ring as a result of the deformed threads. A steel plug would be the best answer. Anything you put on the threads will be cut by the threads and you could end up with bits and pieces floating around looking for a valve to clog or stick into.

[wvkeith]

It is from Jack....how did you know?  So I need to get a steel plug made then?

[tat2dman]

Well since the beginning airgun makers have been mating brass to steel,anyway,I`ve talked to Jack about this and he basically said it`s a 1 shot deal,remove the end cap and you have to eplace the ring,he should know the size for you to locate it locally,it`ll probably be metric,if you don`t have a source I can getem locally through a supplier,just have to know the size.Barry

[Avox]

Only if the brass threads are deformed enough to prevent adequate compression of the o-ring. Then you could use a new brass plug. Just be careful it's not over tightened. Try a new 0-ring first.