Re: coring lead


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Posted by bpfink on July 15, 19100 at 06:23:17:

In Reply to: Re: coring lead posted by Lyle Landstrom on July 14, 19100 at 11:13:58:

If you make your mold have a simple box like mother mold to hold it, and then screw 2 pivot bars to it so you can tip/rotate it upside down without jarring drastically you should be able to slush cast them without any core at all.

Several things will determine the success.

1 Make the original RTV mold thick enough that it has some mass (like 1" or so thick)

and can hold it's own without sagging.

2 Pour the metal into a cool mold each time (that may mean to time the minutes between each pour or add a fan blown air stream to the open mold when between pours)

3 Try to pour at the same temperature each time.

4 Time the minutes between each pour and then the turned over evacuation. (and have a small wire probe there to reopen the sprue if needed)

5 etc.

I did about one pour each 10-12 minutes using 2 different sized molds when doing this.

One is about 3 inch dia. and the other was 4 inch dia. They were not lead though, they were linotype metal which is lead mixed with antimony and tin.

They were not balls but 2 small doll like heads so the neck was a natural place to pour out of as this will leave some spot with an open hole. You can maybe also figure out how to put in an RTV plug at the last second and let the last drips reseal that spot also.

Another but much more complicated system is to do a rotating mold with no open sprue. It needs to be rotated in all directions and means a mechanical or motorized plan pattern with 4 points of turning. They make machines just to do that, and one could be assembled from scrap once you saw how it functioned. They turn very slow and keep rotating during the cooling and you put in a very measured amount of metal each time and expect it to all

become the ball. When cooled it also shrinks a little so is now able to be heard with a slight rattle in the mold (though the mold has also expanded a little whith the added heat.)

I would think you would have to let the mold cool down each time to keep it consistant from pour to pour.

No plans

and never did that myself so your on your own here.

Good luck.

Consider it a riddle,

make it a game,

and I'm routing for your team. bpfink

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