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The poor man's sand binder

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ironman:
Hi everyone

Here is an alternative to baking, gassing and using two part resins when making sand cores.

I use portland cement 9% and water 4% by weight and leave it to cure for 3 days. There are fast setting cements like Ciment fondu but are more expensive than portland cement.

To gain full strength cement needs 30 days to cure but full strength it not always welcome so the 9% cement and 3 days to cure are optional.

If you use over 4% water drying the core is essential. I would not go over 4% water until you have some experience with this method. Have a look at the video.   

     

vtsteam:
Thank you very much for that, Ironman.  :bow:  Just what I needed. And great results with your casting finish!  :clap:

My earlier mistake was trying to extrude it from the core box before cure.

One nice thing about the cement core I see is that you need no vent through the core.

Baked molasses water and flour core binders produce gasses. The cement core doesn't seem to. It's tough pushing a vent wire through a long small diameter core without hitting the sides of the core box. Eliminating a through-vent will make these cores much easier to make.

I also like your method of springing open a slit core, rather than using clamps to keep a wider slit closed. Simple.

One question -- for your facing sand on the exterior, what mix are you using now.? Wonderful surface finish!

ironman:
Nothing has changed, have a look at my video "How to make cast iron molding sand". I use that mix to cover the pattern only. Over the years the sand becomes darker until it is a black colour.

Two weeks ago I threw out all my iron sand (750kg) I went to a quarry and purchased a trailer load of new sand, so that is the reason why my sand looks different. A friend who does casting picked up the old sand from my home and used it to fill the holes in his gravel driveway. He made a comment saying it was a waste using the old sand for that purpose.

vtsteam:
So you use the same fineness of sand for the facing sand -- it just has the seacoal in it, while your main sand has none now.

What grade of sand do you use for your regular sand  -- or is it graded at all? I guess coming from a quarry it is natural mixed sand.

ironman:
I just ask them for their finest sand and I use that sand for both. There is no point having two sands, one finer than the other when it works for  both. I have priced foundry sand in 50kg bags but why buy it when sand from the quarry is 40 times cheaper.

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