Flame cutting cast iron

[marka12161]

Maybe a dumb question: Can you cut cast iron with Oxy-Acetalene? Since you're basically oxidizing the metal i would think you could. Second, maybe less dumb question: If you do flame cut cast iron, are the thermal stresses imparted such that the CI is no longer suitable for use in making/scraping parallels, set up blocks etc?

 

[jspivey]

Although I've never dealt with flame cut cast iron, I would imagine that you would need to normalize/anneal afterwards. That should be enough to remove stresses from cutting. If done correctly, the material should be perfectly usable afterwards.

 

[just Dave]

Maybe a dumb question: Can you cut cast iron with Oxy-Acetalene? Since you're basically oxidizing the metal i would think you could. Second, maybe less dumb question: If you do flame cut cast iron, are the thermal stresses imparted such that the CI is no longer suitable for use in making/scraping parallels, set up blocks etc?

I have seen very crude melting and breaking of cast iron bearing mounts in repair situations. I have never seen smooth cast cutting with oxy/act . I prefer a band saw for all possible cutting jobs

 

[Luke Rickert]

I think it would be really unpleasant to machine after flame cutting, it cuts easily with saws of various types, even using abrasive cut off disks work quite well although they make a huge mess.

I have worked with plenty of old "reclaimed" iron and it is generally stable enough as is but I haven't torch cut any of it. (It tends to be better than continuously cast bar at least)
Luke

 

[DDoug]

I like scrapping stuff with cast iron pieces, the bolt heads blow right off, the cast iron is nick free.
Old Oxy cutting book shows "severing" cast iron, but not a good cut.
Air arc might work, try plasma as well.

 

[dgfoster]

Can you tell us a bit more about your intentions? You must have access to an old machine or table that is too large to cut with some sort of saw or abrasive blade. But, I will point out that cast iron's propensity to fracture could work in your favor. For instance, even on a fairly thick piece of iron like maybe 6 inches it might be possible to use an abrasive saw to deeply score an it inch or two along the desired cut line and then (as people have done for thousands of years in stone cutting) drive a series of shallow angle wedges into the crack along the length of the score. You can develop enormous forces that way and the score will serve as a stress riser. Understand that I have never done this and, yes, if you were nearby I'd drive over to give it a go because I'd love to see how it would work.

However, as I do have a small cast iron foundry where I cast straight edges I, unfortunately, have had occasion over the years to break up many failed Grey Iron castings. (Ductile or malleable iron will never crack using this method.) It has always impressed me how just a small scored stress riser makes the iron break so much easier simply using a sledge to bash it. If I were serious about a thicker section, I sure would make up some wedges and try it.

Whatever distortions in crystal structure you might induce in the iron by flame cutting they should not extend deeply into the iron. So, if you intend to just separate a convenient-sized chunk from a larger mass, I would guess changes in hardness and stress would not extend more than an inch into the metal. So, if you could cut out your piece into a manageable over-size piece and then saw it or mill it to spec, you'd probably be ok. Caution: I would expect you would form white iron at the burned interface. That iron will be in the 60+ neighborhood on the Rc scale. So, you may need to grind away or abrasive saw a kerf to begin saw cuts. Otherwise you will ruin your band saw blade. Simply testing with a sharp segment of an old file will reveal when you have gotten through the hard layer.

Simple 1150F stress relief should do for the net piece though full-on annealing at 1750 would be sure to remove stress and white iron.

Tell us more.

Denis

 

[marka12161]

Thank you all. I have an old Universal HBM that needs way too much work. Buying it was a failed experiment with an on-line auction. I will most certainly remove the table and use it as a work table for all to envy. i'll also remove anything else useful like handles, spindle, shafts, maybe even lead screws. The shafts and screws are plenty worn but will make good fodder for the scrap bin. Regarding the cast iron, I'm particularly thinking about cutting up some of the saddle. I would probably make some parallels and set up blocks for the my smaller mill and shaper, maybe even a base for a height gage. It's always good to have bits of cast iron around for repairs of old machinery. Based on the feedback, I'll use my porta band, angle grinder and maybe even asaws-all I like the idea of scoring the CI and then breaking it with wedges and a hammer. Anything i can salvage is an upside vs just sending it to scrap. I imagine i'll end up with about a 5 gallon bucket of various fasteners as well.

 

[Phil in Montana]

Real simple NO...Phil

 

[Tyrone Shoelaces]

I’ve been involved with shortening large lathe beds. Obviously they were made from cast iron. The welders working on the job used gouging rods. I’ve never heard of anyone used oxy/acetylene or oxy/propane to cut cast iron. The gouging rods worked fine, the castings just needed cleaning up with a large angle grinder after.

Regards Tyrone

 

[David_M]

My old Lincoln welding book discusses using iron powder injection to cut cast iron (and stainless steel). This was iron powder, not containing carbon. Would this be practical? I doubt it.

 

[guythatbrews]

An oxygen lance will do it but probably won't be pretty. I think they are mostly used for demo.

 

[dgfoster]

Thank you all. I have an old Universal HBM that needs way too much work. Buying it was a failed experiment with an on-line auction. I will most certainly remove the table and use it as a work table for all to envy. i'll also remove anything else useful like handles, spindle, shafts, maybe even lead screws. The shafts and screws are plenty worn but will make good fodder for the scrap bin. Regarding the cast iron, I'm particularly thinking about cutting up some of the saddle. I would probably make some parallels and set up blocks for the my smaller mill and shaper, maybe even a base for a height gage. It's always good to have bits of cast iron around for repairs of old machinery. Based on the feedback, I'll use my porta band, angle grinder and maybe even asaws-all I like the idea of scoring the CI and then breaking it with wedges and a hammer. Anything i can salvage is an upside vs just sending it to scrap. I imagine i'll end up with about a 5 gallon bucket of various fasteners as well.

Please let us know how the score/cracking works. You are probably aware of a fair number of YouTube videos detailing the process in stone work. Like cutting stone I would be willing to bet you will hear the cracking as a ripping sound as it progresses in iron.

If you have access to a mag drill, you might consider making a score and along the score using actual stone cutting wedges and feathers which are available for not much on the Web. I’m probably going overboard on the splitting. I’ll admit I find the idea intriguing. Iron does great in compression, but not so well under tension

Denis

 

[guythatbrews]

Using an oxygen lance. The cut looks surprisingly good. They make smaller ones. The first cut might be fun but it would get old very quick. I'll bet it would be spectacular at night.

 

[jim rozen]

Buy, rent, or borrow a plasma cutter. Does a great job.

 

[dgfoster]

Buy, rent, or borrow a plasma cutter. Does a great job.

Two questions:
What is the max thickness of cut in CI with a commonly available plasma cutter?

Does it leave a nitrided (hard as woodpecker lips) crust like it does in steel?

Denis

 

[john.k]

Melted cast iron runs like water ......most economic for heavy iron is arc gouging ......generally you dont need the air blast ,the iron just runs out of the cut ..........so I d say alls needed is a high amp DC source ,and a holder for arc carbons........do wear adequate footwear however ,I once barbecued my foot when a stream of iron burnt through leather and deposited in my instep ......burn down to the tendon ,but not thru it fortunately.

 

[marka12161]

Melted cast iron runs like water ......most economic for heavy iron is arc gouging ......generally you dont need the air blast ,the iron just runs out of the cut ..........so I d say alls needed is a high amp DC source ,and a holder for arc carbons........do wear adequate footwear however ,I once barbecued my foot when a stream of iron burnt through leather and deposited in my instep ......burn down to the tendon ,but not thru it fortunately.

Sounds horrible.

 

[Scottl]

When I was young we used to bring cylinder heads etc. with broken off bolts to a local master mechanic. He used a cutting torch to burn the steel out of the cast iron and left the threads intact, requiring only chasing with a tap. He said the secret was to never release the oxygen lever until the last bit was gone.

 

[dgfoster]

Two questions:
What is the max thickness of cut in CI with a commonly available plasma cutter?

Does it leave a nitrided (hard as woodpecker lips) crust like it does in steel?

Denis

I was thinking maybe we'd get some other responses to my questions. But, none seem forthcoming.

So, I did do some searching for answers. It looks like 2" is about the max a common several thousand dollar Hypertherm can do. They do make industrial machines intended for CNC applications requiring 480V 3-phase 80KW power supplies that can cut up to 6 inches. Hypertherm says that plasma is a good option up to 2 inches but O/A is preferred over that for most situations.

It does look like plasma cutters also produce a very hard surface on CI. That is due to nitriding as a result of atmospheric nitrogen coming in contact with the super-heated surface of the cut metal. That might be mitigated by using an inert cover gas like argon.

 

[metalmagpie]

You can't ignite the cast iron the way you can steel. You can kind of melt your way through but it will be uglier than butt ugly.

I spent 10 years as a shipfitter where a torch was my #1 tool. I have done severing cuts on cast iron. Clean torch cuts are not possible. If you try, you will use a huge amount of fuel gas too.