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Chucks and the minimum diameter they can grip

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  • Chucks and the minimum diameter they can grip

    My 6" 4-jaw won't grip anything smaller than 3/8" in diameter. I need a 3-jaw, so I figure to buy a smaller size.

    Is there any rule of thumb on the lower end of gripping capacity?

  • #2
    Just get more pointed jaws for your chuck.
    Andy

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    • #3
      Or, make pointy soft jaws.

      Or, get a collet chuck instead of a smaller 3-jaw. It'll have less runout than a 3-jaw if mounted carefully and you get good-quality collets.

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      • #4
        My Bison 8" 6 jaw will grip down to 5/16". For anything smaller I use a drill chuck mounted in a 1" solid socket.

        JL..................

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        • #5
          Buy a 3" chuck, and chuck it in your 4-jaw chuck.

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          • #6
            I used to chuck a Jacobs type chuck in the big chuck to grip real small diameters. You can still indicate the part in to get it to run true. I mean the type of Jacobs chuck you use in the drill press,or tailstock.

            Now I have another lathe for smaller work(Hardinge HLVH) that uses collets.
            Last edited by gwilson; 08-13-2011, 11:59 AM.

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            • #7
              Originally posted by JoeLee
              My Bison 8" 6 jaw will grip down to 5/16". For anything smaller I use a drill chuck mounted in a 1" solid socket.

              JL..................
              Take out every other jaw in a six jaw and the jaws will almost meet.
              Jim H.

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              • #8
                It isn't a six jaw the OP is describing,though.

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                • #9
                  This is my 250mm (9.84") Pratt Burnerd Super Precision 3-jaw scroll chuck. It' seems to be able to hold down to somewhere around 4mm (.156") quite securely. And, near-zero runout no matter where it's measured.

                  It was sold to me by a former employer for $250, never had been on a machine.

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                  • #10
                    A friend of mine sculpted out a set of soft jaw for his three jaw so it accepts 5 C collets. Works pretty good and he saves several hundred $.

                    Chucking a 3" three jaw in a larger 4 jaw works well for small sizes too. You can adjust the 4 jaw to exactly center the three jaw.

                    I suggest bolting the three jaw on a disk of 1/2 thick round stock made to fit but having a 1/4" larger OD for the 4 jaws to grip on. The disk takes the abuse of the jaws and not the smaller chuck body.

                    I have a couple dozen split bushings I've made over the years for different things including a number that have been tapped. I slip them in the three jaw for smaller work or bolts I have to grip to mod the head.

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                    • #11
                      For really tiny stuff, I've put the small rod in pin vises and then chucked the pin vise in the lathe.
                      VitŮŽria, Brazil

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                      • #12
                        Forrest has it......

                        That's what they make collets for
                        1601

                        Keep eye on ball.
                        Hashim Khan

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