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303 stainless cracked after boring

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  • 303 stainless cracked after boring

    Just spent $100 on 2metres by 1 inch of 303 stainless bar. Cut off 50mm with my ancient power hacksaw, put it in the 3 jaw and drilled and bored out to 15.85mm to fit a shaft. I was just admiring the snug fit(still a novelty for me) when I noticed a crack extending along the whole length which extended through the wall of the bored part. It was up to 0.5mm wide in places
    Did I do something wrong or is the metal dodgy?
    Regards
    David

  • #2
    At a guess, I'd suspect that unless you were using flood cooling the heat stress on a wall that thin in a three jaw was the root cause. 303 builds heat at the cutter tip so where that thin wall is gripped by a jaw it can create quite a heat stress line down the work bore.

    I could easily be way off on this guess, I just know that 303 likes flood cooling when being worked.

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    • #3
      You might get better results by cutting a longer piece so 2" sticks out of the chuck. Turn the OD to the final size, drill/bore the ID, and part off.
      Any products mentioned in my posts have been endorsed by their manufacturer.

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      • #4
        Possibly a stringer (slag inclusion).

        Have a look elsewhere on the bar, using a magnifying glass.

        The stringer (if that's what it is) shouldn't be very long, so make the next sleeve from the other end of the bar!

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        • #5
          Crack

          That sounds like a bad piece of material to me. 303 is soft enough it shouldn't crack like that.

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          • #6
            'snug fit' Do you mean it sliped on with hand force, or was it a press fit you hammered/pressed on?
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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            • #7
              Defective material.
              Gary


              Appearance is Everything...

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              • #8
                and the winners are

                all the people who voted for a defect in the metal. Went to the supplier today who sugested ( as several people here did) to check the bar i cut the 50mm bit off. Sure enough there was an identicla crack extending about 300mm up the bar. They are going to replace the bar and threw a huge bit of leaded free machining rod for nothing.
                If you send a self addressed envelope you will receive a hand engraved Steinlager bottle top as a prize


                The marks in the mill table were done by the previous owner
                regards
                david

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                • #9
                  Thanks for the feedback.

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                  • #10
                    bigger picture , I hope

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                    • #11
                      In sheet its called a lamination, probably the same in bar, the crap in the crack is normally slag/al203/mould powder from the billet caster, it arrives due in part to mis alligned rolls in the caster, could be a segment out or a support bearing failed, the solidification requires a 'head' of ferrostatic pressure to feed the solidification point, if the billet gets to hit a bump the head of pressure gets cut off and a centre line lamination occurs.
                      Glad they fessed up and dropped you a bit of bar!
                      regards
                      mark

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