Jack Grieve (sorrentinacoffee) just let me know that the issue with my boiler plug is that the machine was intensely polished with the plug in. This melded the aluminum from outside the plug with the plug itself. He says on the Sassoon the plug was polished separately and then inserted. It may not be necessary to remove the plug since I can descale. If I do remove it, I could find a fiber or asbestos gasket that is difficult to remove. I will post more on this if I make another attempt to remove the plug. First I am waiting to receive new gaskets for the Robbiati Atomic, which should seal it well for brewing and steaming. If not I'll want to service the brew pipe, which may involve removing the plug or accessing the pipe through the brew head using a long cleaning brush.

drgary wrote:Jack Grieve (sorrentinacoffee) just let me know that the issue with my boiler plug is that the machine was intensely polished with the plug in. This melded the aluminum from outside the plug with the plug itself.

This statement is questionable.
It would not make sense then when the knob is left screwed (I hope I am using the right word...)for several years and it gets "welded".
I think the calcium and magnesium salts dissolved in the water create a galvanic corrosion which fix the two parts together.

Ah, okay. Thanks! If you look at the photo closely, how do you explain the concentric rings? Was polishing taken to the point that it wore off the outer surface and exposed threads further in?

Lvx wrote:This statement is questionable.
It would not make sense then when the knob is left screwed (I hope I am using the right word...)for several years and it gets "welded".
I think the calcium and magnesium salts dissolved in the water create a galvanic corrosion which fix the two parts together.

Ah- once again I am 'questioned!

However I think you misunderstand: what I said is- when the machine is first cast- the plug and seal are put in Before the machine is polished. At this stage the surface is quite rough following sand casting. It is then intensely polished and in that process the plug and body can become a little melded together... polishing is actually one of the biggest jobs in making one of these machines... you will see this plug melding on robbiati atomic but not sassoon atomic- Sassoon clearly polished before plugging...

After that it can be 'welded' by galvanic corrosion but that's another matter- and usually they do easily unscrew with the correctly sized tool...

sorrentinacoffee wrote:Ah- once again I am 'questioned!

I'm glad to know technically how one of these plugs can get stuck because that's the first step in figuring out how to fix it (or in my case leave it alone). BTW, knowing Lucio, I think he is only making a technical point, and the wording is challenging in English.