tmuir
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Why reproduction SVs & OF plugs may not screw in properlA while ago I bought a reproduction safety valve for my Bowman loco and it would not screw all the way down and I could not figure out why.
Tonight I made a new filler plug for one of my engines and was surprised to find it would screw down on one engine but not another.
After looking at a couple of original parts it struck me.
If the thread is longer on the reeproduction part that the bit it is replacing it may not screw down. Here is the reason.
The thread on the original part may not of screwed right through the bush leaving a turn or two of the thread in the bush exposed to the inside of the bush. Now over the years (or decades) of use the exposed threads get caked up with calcium and crud just like the rest of the inside of the boiler.
Now when you come to screw in your replacement part and the thread is longer it needs to screw through the part of the bush that is full of calcification and just won't go.
The solution is to get a tap of the correct size and just in your fingers screw it in. When you do this you will see a lot of white 'stuff' come off onto the tap. This is the calcium stopping the part from doing up and after that it should all be fine.
Just did it to two bushes on my engines and now the repro parts screw all the way home.
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bessytractor
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thanks for the tip Tony,
something well worth knowing!
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johnreid
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A lazy approach might be to double the thickness of the Gaskets, but still prone to leak I bet.
It can be difficult to find the right size Tap at times.
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tmuir
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| johnreid wrote: | A lazy approach might be to double the thickness of the Gaskets, but still prone to leak I bet.
It can be difficult to find the right size Tap at times. |
LOL
Thats what I did on the Bowman because at the time I couldn't figure out why it would not screw home.
Most of the tap sizes used on toy steam engines seem to be uncommon sizes that you have to specially order which is a pain.
I think if I do start selling parts I will be recommending people to buy a new bush too so they can just replace the old one.
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MamodFan
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one of my bowmans has been tapped with a taper tap thus it does not have the correct form all the way through. The threaded part of a real bowman sv is very short so it screws in.
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