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Hazards of Unknownium

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  • Hazards of Unknownium

    Went scrounging thru an old box of junk my Dad had left me, looking for things to put into the lathe to practice on. Found what looked like an old piece of rusty shaft about 5" long x 1-1/4" dia. Tested with file and seemed fairly soft.

    Chucked in lathe and knocked most of the rust off with emery cloth. Started cutting to true up diameter and after got down to good, clean metal was turning very nicely. Tiny blueish 6's & 9's.

    Got diameter good and faced off the end. Flipped around to face other end. Started well until I got near the center. Insert started squealing. Backed out, checked insert, more cutting oil and tried again. Got near center and squealed again.

    Pulled piece out to examine and all I saw was that the center 1/4" was REALLY shiny. Took it over to belt grinder and this is what I found.



    Notice difference with the center 1/4". Used a spring punch to check for relative hardness. Mark in outer area easily seen while mark in center is barely visible. Don't know what it is, but it's harder than woodpecker lips.

    Put back into lathe and cut down to center piece with hacksaw about 1/8" back from end. Removed with vise-grips.



    Lesson learned - 1 damaged insert and the lingering question of "What was this in its previous life?"

  • #2
    My guess is that the core is carbide. Some boring bars have carbide core in order to increase dampening.

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    • #3
      I doubt carbide, However just about any really hardened metal will mess up a standard carbide insert. Im thinking it was a pin pressed in to keep the metals togethor... Hardened pins won't bend. (they just snap yes, But they snap at a much higher force then would of taken to bend a soft pin)
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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      • #4
        Since it is an offcut of who knows what, I will hazard a guess. It could be a section of bar used in frabricating jail cells. It is supposed to have a hardened center to discourage hacksawing.
        Duffy, Gatineau, Quebec

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        • #5
          It looks like a dowel pin to me.
          It's only ink and paper

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          • #6
            It would be rather difficult to have a hardened core the length of a long piece wouldn't it? Sort of the reverse of case hardening. Maybe it is just a dowel pin and you just happened to hit it.
            "Work hard. Tell everyone everything you know. Close a deal with a handshake. Have fun!"

            -- Harold "Doc" Edgerton

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            • #7
              I found an inclusion in a piece of thick walled 5" pipe the hard way. This pipe is domestic and was made to a structural code originally. I have used a lot of it and not encountered this problem before. It machines very nicely so I will probably continue to use it,but I will cut it into on the band saw.
              Byron Boucher
              Burnet, TX

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