Using RTV for No bake sand core boxes?

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myrickman

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Am working on a core box for an engine cylinder head. It is a one-off affair, so I am trying to do this the easiest way. Am going to use the actual head from another engine as the outer pattern (adding material for shrinkage) and am making up a core pattern for the passages. The foundry I go to uses no-bake core sand. Question is can I make the core box mold from RTV? I can house the RTV in a wood box to give it rigidity. If so, making the parting lines for the core box would be real easy with a sharp knife. Comments/suggestions?? Tried to search this on the internet and found zip.
 
Most room temp vulcaninzing RTV will break down around 450 to 500 F. There are high temp varieties that can go up to about 700 to 800 degrees for short periods.


Molten metal would make quick work of it I'm sure. Wouldn't plaster of paris with the mold sand work better for a one off?
 
Alumilite has many varieties of RTV's for diff. applications. I use the same RTV mold for casting plastic & 500 deg. pewter. Pretty tough I can't tear it by hand & the part detail is great. Some RTV can do zinc but it breaks down rapidly.



 
The RTV is meant to use for the core box mold. The core pattern is somewhat complicated and with RTV I can simply splash over the core model in layers and allow easy removal. The core box made from RTV will be supported by wood sides to maintain rigidity. Of course, RTV will obviously not handle cast iron!! I already spoke to my foundry guy and he is game to try it.
 
The foundry is making the cores from my corebox. The paper you suggested Tin is excellent! I am a materials person by trade so it was right up my alley. After reading the article, I might try my hand at it.
 

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