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Dealing With Hard Spots in Iron Castings

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My family started having castings made for hit and miss engines back in the early 70s. I can still recall Progressive Foundry at Perry Iowa USA, after going in the front door and up some 3 steps to a little room off to the side, we met the owner. Now one needs an appointment and they have about 10 minutes for me. But always very glad to help some one playing I call it with iron.
   Now it is a huge factory foundry that only uses one sided match plates where they make two halves and glue them together. They charge $250 per hour plus costs. And they charge to change the plates. Casting cast iron 3 days per week and ductile 2 days. They town has boomed now with hispanic workers who also work a the huge meat processibg plant. They cast Ford drivetrain parts for one thing.
   I still go there and mooch materials. Once, while there a guy walked up and showed a casting to the metal mixer man, it was broke in half, the main way to look at the grain.  It was silver white about 1\8" all around. The guy just said, "some one did something wrong". Looking at their scrap pile they had precharged loads ready to melt. They use a huge electric furnace which means an open pot maybe 10 feet across and 15' deep?
   But anyway, the scrap charges included new cast iron ingots, scrap castiron, and shreaded auto steel, which now means everything imaginable. I scrap some, and have noted they drag the more expensive 3' prepared steel and 5 foot number 1 over to the shreader and push it through, mixing all of it together, after hours so no one knows they lay 30 cents in the dollar for what they sell for all one price.
   The melting pot has an up and down meter input that had 2 prongs a set distance apart. Through the electric current a screen off to the side had graffs which stated all elements in the mix. Pretty smart! In the old days they cut 1" cubes, then placed them on the surface grinder and flattened them perfectly.
   They then placed a single drop of Nitric acid on the iron. One could smell that outside. Nasty stuff. They then held the piece up to a poster that resembled a map of the universe with set cubes all over it. Each picture-cube had either little red dots, half moons or other shapes. With a symbol chart in the corner, one would determine what the iron held. Silicon, Manganese and other elements.
    When casting all molds are like in groups, so they can dump any bad iron used molds, the first thing poured are little molds with wedges cast in them. They put them first, which casts a knife blade wedge and then they break it. If it is silver for more than maybe 3/32" they dump the whole pot into a pig mold. So they have pretty good quality control.
   I have some other interesting comments, will post later.


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