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A Tale of Two Castings

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That looks real professional quality!

Thank you kindly, Pekka!  :beer:

Today, instead of doing the same casting a third time, I wanted to try something different as an experiment. I have a lot of old sprues and problem castings from 9 years ago when I first tried iron. I wanted to see if any of that was usable with careful slagging (it had a very difficult pasty slag back then), and also I wanted to try a smaller more complicated casting, and see whether I could get small pattern details. Also whether smaller castings could be kept soft enough to machine well.

So I tried using the old junk iron on a pattern I made a few years ago for a Westinghouse style twin cylinder steam engine block.

The slag was again horrible, and I probably should have added a little sodium carbonate to liquefy it better. I've been mostly avoiding that because it attacks the crucible. But added just before the pour minimizes the problem. Anyway, here is the result of today's pour.

Again I did lose a little definition and added finning because of the weak bond strength of the sawdust facing sand. But actually, pretty good detail definition in a small casting. I'm looking forward to trying hardwood sawdust instead of this older spruce stuff.

tom osselton:
That looks good. When you pull the dross off what do you use for a lifter?

Tom I don't have a picture of it tonight, I'll get you one tomorrow.

I am using two, one for while the crucible is in the furnace, and a second smaller one of different shape for immediately after I've set it in the pouring shank. The bulk of the slag comes out while in the furnace with the long skimmer -- which does a crude job. The smaller skimmer gets whatever has been missed just before pouring.

Interesting point, Tom, btw, there's a relatively huge loss in casting iron compared to aluminum and zamak. I'd say 35% in general, loss of metal, comparing part, gate, sprue, weight after casting compared to weight of scrap iron put into the crucible. It's a lot easier to underestimate than other metals, I've found.


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