Casting a Gingery Lathe

[Nobody Special]

3 hours ago, Frosty said:

Congratulations! Did I miss it when you told me you were pouring the mold in that orientation? Or did you try it in the reverse without success? 

If you try it again flip it over so the runners, gates and pour cup are on top so the al doesn't have to flow to the bottom and be forced up into the casting like that. The melt cools in the runners, risers, gates, etc. and you want the melt flowing downward in the mold, not upwards from below.

To get it to flow upwards you need to have the greater mass at the lowest point so it doesn't start to solidify before the entire mold is full.

Frosty The Lucky.

 

Maybe? I probably missed something. I really, really thought about doing the casting inverted, which would have made several things easier, not the least of which was drawing the pattern out cleanly (most of the castings had varying levels of fins on the gated side from edge damage). However, I couldn't figure out how to get the sand cores out clean, invert them, and suspend them in just the right place so they were off the "top" of the pattern.

I don't think I'm good enough to play with chaplets yet. Worse, the cores weren't baked in this one, so they were fairly delicate. At one point I had made some I had treated with molasses water and baked, but something was off - they had expanded a bit and didn't fit into the pattern without forcing them, which of course made them come apart. I might could have shaved them a bit, but by that point they were already broken. They sat overnight, so I suspect maybe they drew water from the air.

Got the same problem with the hollow feet, which is the next step while I wait until I can get to the mainland to get some big enough cold rolled for the ways and as a reference surface to scrape the bed. This island really, really needs a steel supplier.

[Frosty]

Ram it up like you do now but with the runners in the other half and cut your sprue, riser, etc. in the other side and turn it over to pour.

Maybe add a pinch or two of finely divided fiberglass to the sand to give it some bridging strength or a LITTLE water based glue like Elmer's to the moisture in the sand. Keep it covered air tight until you ram it up of course but it'll add some stiction strength. 

What's to understand about chaplets? You know in advance how thick the large flat is, break up one of the failed castings into LITTLE pieces and space them to support the core in positions that won't interfere with the melt's flow. If the caplets are small enough they'll just be incorporated into the casting. It's not like the core will sink when the chaplets melt, hydraulics will prevent it or slow it to the point the al will solidify before the core can move.

Frosty The Lucky.