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Centering Round Objects in 3 Jaw

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  • Centering Round Objects in 3 Jaw

    Some time back one of you smart individuals posted a roll / ball bearing
    mounted on you tool post to gently center a object on a 3 jaw chuck.
    I don't have the roller made yet, but I need to center a object the other
    day and said "hey I know how to to that". So I put my knurling tool in the
    quick change and left the part slightly loose. I advances the knurling rollers
    and low and bhold I was ready to turn the part.
    Thanks again to the individual who post that wonder idea, and all the
    guys that chimed in with their versions.
    You guys sure have some GREAT ideas.
    Great forum.
    Thanks!
    olf20 / Bob

  • #2
    Pushing the end of a part does not change the run out of a scroll chuck at the jaws. I makes the part not run out at a particular position,
    If indeed you require a very high level of precision use 2 indicators, one at the chuck and one at the far end of the part. Adjust the chuck accordingly.
    If you do not have an adjustable scroll chuck use a 4 jaw instead.

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    • #3
      Yeah but it's a great tip for non critical things. I needed to put a put a small chamfer on of a bolt today, so I chucked it lightly, used the roll center and had it running plenty true enough in seconds. Snugged, turned done. It's a great tool.
      21" Royersford Excelsior CamelBack Drillpress Restoration
      1943 Sidney 16x54 Lathe Restoration

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      • #4
        Not really "centered" as in axially. Instead the "face" was "trued" by the wheel's action.

        And yes, it's a darn handy thing. Especially with relatively flat disc line shapes that only span one or two of the "teeth" on the jaws.

        It's not the idea of any of us though. I saw the idea about 20 years ago in one of Guy Lautard's Machinist's Bedside Reader books. And he admitted that it was a very old idea when he learned of it.
        Chilliwack BC, Canada

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        • #5
          Well? Some times bented I might agree. JR

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          • #6
            Originally posted by BCRider View Post

            It's not the idea of any of us though. I saw the idea about 20 years ago in one of Guy Lautard's Machinist's Bedside Reader books. And he admitted that it was a very old idea when he learned of it.
            The idea has probably been around since the wheel was invented. In fact, it may be the reason the wheel was invented in the first place.

            Some cave man thought, "ya know, I could straighten things up better in my three-rock chuk if my stick had a roller on the end...." And the rest is history.
            Lynn (Huntsville, AL)

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