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Identify Cast Iron in scrap pile

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  • Identify Cast Iron in scrap pile

    What is the best way to identify clean machined cast iron (no raw surface) in a scrap pile. Assume no spark test available (I suppose I could take a cordless grinder, or angle grinder, but...). I know there is some variability in magnetism, but not clear cut. I have a friend who gets paid to clean out storage buildings and the lot. He sometimes looks the other way as I go scavenging (it's his company, so not theft) as long as I don't start getting into hundred weights, and as long as I don't start bringing friends. I've got some pieces that are visibly cast iron due to visible "grain", but I think that's generally "low grade". How would I identify the good stuff like nodular and so on if I can't see any casting surface?
    Russ
    Master Floor Sweeper

  • #2
    A cordless drill and a bit,nothing drills like cast,look at the swarf.
    I just need one more tool,just one!

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    • #3
      Originally posted by wierdscience
      A cordless drill and a bit,nothing drills like cast,look at the swarf.
      Seems like a good approach. What is the swarf from ductile iron like in comparison? Still like plain cast iron or more like steel?
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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      • #4
        Re: Cast iron

        If you pick it up and tap it with a hammer you should be able to tell by the tone of the ring. Steel makes a high pitched ring but all the cast I have ever seen makes a much lower tone.
        Jim (KB4IVH)

        Only fools abuse their tools.

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        • #5
          I should have siad, "Preferably non-destructive".

          The drill idea is a very good one. But I just KNOW that if I put even a very shallow hole in a nice piece of cast, it will be right in the wrong place when it comes time to use it.

          Good point on the tone of the ring too.

          Thanks...
          Russ
          Master Floor Sweeper

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          • #6
            Bite off a little chunk for a taste test.
            Surely CI and all the various steels each have a distinctive flavor.

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            • #7
              Originally posted by Scishopguy
              If you pick it up and tap it with a hammer you should be able to tell by the tone of the ring. Steel makes a high pitched ring but all the cast I have ever seen makes a much lower tone.
              Ditto. Steel has twice the damping coefficient of aluminum, ductile cast iron twice the damping coefficient of steel, and grey cast iron twice that of ductile (which is why it's used in machine tools, even though it's not as strong as ductile or steel).

              If you whack on a piece of good grey cast iron (like DuraBar or VersaBar), it'll make a dull thud. Steel will ring.

              If you can find a broken piece, you can usually tell ductile cast iron by the little dots of graphite. Grey cast iron has little streaks (flakes) of graphite.
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #8
                Yeah, identifying broken is generally no problem. But this place scraps a lot of old out dated fixtures. Most are steel, but I've seen some that I strongly suspected were CI, but given the tools at my disposal there, and a desire to both not damage the piece or annoy my benefactor, I wasn't quite sure what to do to figure out if my suspicions were correct. I should have thought of the damping quality, but it didn't occur to me... <sigh>

                As for the taste test; hmmmmm... I think I'll pass on that, particularly the part about biting off a piece. Seems to fail my "non-destructive" test; for both the piece and my teeth...
                Russ
                Master Floor Sweeper

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                • #9
                  Yeah, the taste test ... it was just a thought.

                  Though I think that's how they did it in the old days.
                  Too bad Millman's not around. He could verify that.

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                  • #10
                    I'd agree with the small hole being drilled , also might add that looking at the shape of the part might help too. Parts that would require a lot of fab would usually be cast, if put into high production volumes. Then again, a part taking more stress might be cast in steel.

                    Just a thought...
                    I bury my work

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                    • #11
                      For the most part, none of this will be production, it's almost all fixtures from manufacturing. Lots of nicely machining tool steel (if you don't mind a few holes here and there), quite a few aluminum bits including some rather large base plates, lots of camp clamps and strap clamps along with some nicely made handles and knobs, etc. But there are some pieces of material that seem like steel but just don't look/feel quite like the rest of the (mostly) tool steel. Much of this that catches my attention winds up being well pocketed and worked larger "blocks" (seemingly not cast, perhaps durabar type material?) used for unknown duties of the past. But some similar material still has large chunks of solid that might be useful for small projects where a CI bearing surface or damping might be useful. Yeah, I know, "mystery metal woes" and all that, but the price is right.
                      Russ
                      Master Floor Sweeper

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                      • #12
                        Scrap Envy

                        I'm jealous. I used to have access to scrap goodies when I worked in tool and die. At the end of a job there were always lots of little blocks, cutter blades, and cylinders of heat treated A-6, A-2, D-2, and H-13 lying around. These bits made excellent setup blocks and parallels. We would grind them and make matched pairs for use in machine setups. If we wanted to make a sine bar or something more complicated and the work load was not too big, the tool room guy would give you enough stock to make what you needed and the foreman would send it along to the heat treater with the next load of die steel to be done. Ahhh, the good old days.

                        I recently lost my "junkyard connection" since my wife's cousin just sold Clearwater Scrap Metal. I used to get all kinds of great stuff from there.
                        Jim (KB4IVH)

                        Only fools abuse their tools.

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