Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I've acquired a rathe large Doll steam engine. There's one problem. Under the dome is a fitting
that has undersized threads that are buggered. Someone had tried to solder it but it didn't take.
I have it out and the threads in the boiler are OK, not beautiful, but they work and hold when I
screw in the filler plug or whistle. They screw in fine and tighten down good. Now the thread is
an old metric, odd size, 7.2mm x .08 thread. I really don't want to try to solder it back in and
take a chance of loosening the thread nut inside. I do not want to have to open the boilers end
cap because there is a flew coming through it into the chimney house. Here are some pictures of
what I'm talking about.



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Now I would like some options as to how to remedy this problem. I have thought of using some
J-B Weld higher strength formula but if that fails, I'll have a worse problem. One more thing,
like I said earlier, this bad stem can screw in but before it starts to bottom out it will miss
the threads and you can pull up on it and it will move up and down about 1/16th". It won't pull
out but there will be some play in it.
Any ideas short of "Send it to me and I'll have a look", would be appreciated.
Thank you and stay safe,   
Tommy

Thanks Jim, I'd like to post more pictures and a video but not until I get this going.

Tommy, I am suspecting that you got the Doll 366 poppet valve?
My recommendation is to take the front boiler end cap & do it right.

I know back in this time period the German manufactures used regular soft solder and not silver solder.

Just a heads up, my Märklins from this time period use a mix of soft and silver solder on boilers with flues… not sure on the Dolls?