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The poor man's sand binder

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tom osselton:
 :beer:

vtsteam:
Well as long as we're talking about a poor man's sand binder, we could also mention baked sand cores. They also don't require sodium silicate and CO2, or epoxy formulations, and use common non-toxic inexpensive off the shelf ingredients.

The cement/coarse sand cores work great for cores from an inch on up, but smaller than that and even with wire reinforcing, they have been too fragile for me to use. The other disadvantage is waiting a few days for them to unmold.

I just made a small baked sand core today and it's much stronger then the cement sand version I tried. It also released from its plaster corebox much more readily than a cement sand core, which broke and left residue that had to be carefully scraped out when I tried. Both attempts used mineral oil as a release. I also tried Vaseline with the cement sand mix, but the core still broke, and also left cement residue.

A baked sand core is much quicker to harden also. Depending on size and corebox, about 30 minutes to an hour, compared to several days for cement/sand. The baked sand core below took an estimated 0.15 kWh energy in a small toaster oven, or about $0.03 U.S locally.

Ingredients were molasses water, and dry wheat-type wallpaper paste. Some use corn starch, corn flour or wheat flour, but the walpaper paste was recommended as stronger by D. Gingery, who 20 years ago, through his books, taught me casting, so that's what I use. (btw I think it's considerate to cite sources of information and give credit to people who kindly helped you learn things, so they're not forgotten -- a practice too rarely acknowledged these days.)

I will definitely continue to do larger simple cylindrical cores using Portland cement as shown by Ironman (Luckygen1001) -- it does a great job. You can easily make a number of coreboxes from pipe if you need several at a time. And cast them in advance -- the cores are inert and will last forever in storage.

On the other hand, for small and complex cores, I think baked sand offers a lot of advantages.  A complex corebox may not be easy to make in multiples. You can release the cores quickly onto a core plate, or simply bake them in the corebox, if suitable, and the turnaround is therefore rapid. Storing completed cores does require a little more care long term -- they need to be kept dry, but that doesn't present great difficulty.

Both methods are good to have in the casting arsenal, are inexpensive, and use easy to obtain off the shelf ingredients.

I just made this core yesterday. It's the core for a model Westinghouse-style twin cylinder steam engine. It shapes the spaces for the cylinders and the lower crankcase.

RotarySMP:
You forgot the other big advantage... the smell like cookies when baking :)

Nice core.

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