Machining "cheap" cast iron

[Peter Housyon]

On my Emco 5 Lathe I am attempting to remove the bottom of a cast iron "Dutch Oven" pot. I have broken off the rusted sides and have bolted the jagged bottom to the spindle. I am trying to make a disc. that I can use for a faceplate but nothing seems to cut it properly. I am turning it slowly and have tried HSS, brazed carbide, replaceable carbide tip type cutters and now a cut off tool but I am getting nowhere. Am ready to resort to a hacksaw ! Help.

 

[benmychree]

You may have to resort to a grinder, sounds like a exercise in futility. You should be able to buy a machinable cast iron blank online. I doubt that the bottom of a pot would be thick enough to make a faceplate anyway.

 

[Hawkeye]

You referred to cheap cast iron. It is common in cheaply made items to cool the casting quickly to keep the process moving along. Chilled cast iron can be extremely hard. After all, it contains higher levels of carbon than tool steel. I found out about it when I watched my horizontal bandsaw blade go dull in seconds.

 

[MrWhoopee]

Cheap materials can get expensive fast. Cut your losses and move on.

 

[WCraig]

I'm no expert but my understanding is that cast iron that has been cooled too quickly ("chilled") is extremely hard and basically can't be machined. Possibly, if you build a big bonfire and heat your Dutch Oven to red hot and then heap ashes on it to allow it to cool very slowly, the metal might respond better to machining. Maybe. Otherwise, you may have to use abrasive saws and the like.

Craig

 

[Bi11Hudson]

The iron in a "Dutch Oven" isn't really "cheap", is is just a different metalurgy than what we see as machine castings. And the casting process is different as well. Further, the bottom of the pot will likely be too thin to use as a "face plate". It might make a good weight to counterbalance something, your call there. My advice would be to start with a machine casting that can be machined and be done with it.

.

 

[great white]

Gawd knows whats in cast these days if it came out of china. They buy up all kinds of scrap and dump it in the crucible. Then, whatever comes out is whatever comes out.

Its not uncommon to be happily machining away at “cheap” cast iron and hit a spot thats harder than heck. Try a bedrail sometime. Theres no telling what is where in those things but I’ve routinely hit spots so hard in those things that you pretty much can’t even drive a hss bit through it and even cobalt has to work hard at drilling through.

 

[ericc]

You might have better luck with brake rotors or barbell weights. I have. But, then, I've had my share of hard spots. I have had good luck doing spot file tests. If you find a single hard spot, give up. Even if you don't find one, you could it an internal one. You will recognize it when the sound changes and the cut messes up. Sometimes you can get through these by blasting through with a junk piece of carbide, or by touching it with a die grinder. This is really low return activity, and can end up wasting a lot of time. I have a few nice tools (about four) that I made from junk cast iron. Only one had hard spots.