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  • 4 jaw independent independent chuck

    Had an idea the other day. Uh oh Anyway, since a lot of what I do on the lathe involves chucking slightly irregular squarish pieces of plastic to turn up a roundness to rechuck with to further turn the piece to make a part (did that make any sense) I could really use a chuck where opposing jaws can be adjusted independently of the other opposing jaws. Each pair needs to work like a scroll chuck, in other words they slide in and out in unison as you turn a ring or something.

    So, a chuck like this would have two separate adjustments, one for one pair of jaws, and another for the other pair. Opposing jaws do not ajdust independently as in a typical four jaw.

    Is something like this made? Or will I have to design and build it myself- and any ideas for a design?

    One thing I'm considering is to make it so it mounts in the three jaw. That way I can leave the three jaw mounted, then just clamp this 'adapter' into it when needed. They will both be used together, one after the other, so I don't really want to remove the three jaw and mount this thing each time. Three equally spaced holes in the back of it will allow it to be held firmly enough, and it won't need to be a precision device since all I'm doing is mounting somewhat irregular square or rectangular pieces of varying sizes into it to turn a proper stub so they can then be turned using the three jaw.

    I doubt there is such a device, so the real question is how to I arrange to crank the jaws in and out as independent pairs?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Such a chuck exists,but the smallest is 8" and cost a pretty penny.They are marvelous pieces of tooling,one day I will own one.

    http://www.lathe-chucks.com/BISON/BI...ION-CHUCKS.htm
    I just need one more tool,just one!

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    • #3
      Originally posted by darryl

      I doubt there is such a device, so the real question is how to I arrange to crank the jaws in and out as independent pairs?
      My first vision of design is a pair of leadscrews with RH nd LH threads on opposite ends. It would require two which would have to cross in the middle so the corresponding nuts of each pair of jaw would be at different depths, but that's manageable.

      To get the timing right you'd probably need to mount the jaws, then turn them as in truing a chuck.
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

      Comment


      • #4
        Originally posted by wierdscience
        Such a chuck exists,but the smallest is 8" and cost a pretty penny.They are marvelous pieces of tooling,one day I will own one.

        http://www.lathe-chucks.com/BISON/BI...ION-CHUCKS.htm

        Nope... he wants to independently adjust "opposing pairs"... not all 4. It would need two scrolls...

        I have a 6 inch rohm 4 jaw independent and scroll (like the Bison)... my favorite chuck - almost never use a 3 jaw now. Not sure what I'd ever use an "opposing pairs" chuck for ..

        Even though it doesn't show in the Bison catalog, they do make a 6.25 inch scroll+independent 4 jaw.
        Last edited by lakeside53; 09-21-2009, 11:13 PM.

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        • #5
          I don't think the Bison combination 4 jaw quite matches what darryl is describing, but New England Brass stocks them down to 5". http://brassandtool.com/Machine.html

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          • #6
            Your idea is very interesting. One way (and I am sure there are a lot of others) to quickly chuck a square or rectangular piece for roughing to round is to make a wide and fairly thick split ring which will fit over the piece. Then just tighten it in a three jaw chuck with the split and corners suitably positioned. If the ring is a suitable size and thickness, the jaws will compress it tightly to the work. This will do the job for work of about any shape and has a fairly good size range. Clamping force will be limited so care is required.
            Don Young

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            • #7
              I'm still not sure what two sets of scroll adjustable jaws buys you...

              On my rohm (or the bison)... I adjust each of the jaws to suit the work, then the scroll works on all 4 like any other scroll chuck. I can un-chuck and re-chuck the work all day long...

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              • #8
                What I want to be able to do is quickly center a piece that may be square, may be rectangular, and will be variously sized and likely trapezoidal. It might have three sides more or less flat, then the last side rounded, or it could have one concave side and one convex side, with the remaining sides sort of flat, but not necesarily parallel. Being able to center it both ways allows me to turn it round and have it be as large a diameter as possible once all the flats are turned off. If I can't do this quickly, my next best way is to shim it in the three jaw until it's more or less centered. This doesn't hold very well, so I waste time taking light cuts until I've got all the flats removed.

                Using the four jaw chuck would be fine if all the pieces were the same size, but that's not the case. My four jaw is a bit of a pain to adjust, and that takes up time as well, thus my desire to have this custom chuck.

                It's a tool, and I don't mind making it. It's something that I'd like to have, not an essential. Probably a winter project.

                I can see how to make it work using combination left and right hand threaded actuator rods, crossing at the spindle axis. This merely requires the threaded holes in the jaws to be at two different heights. It won't be hard to center these rids either, it's a matter of using some hollow setscrews around the perimeter of the chuck plate. What I will be missing is the thru-hole, but for this application I can't see needing it.

                Now for the procedure to make these left/right threaded leadscrews- and thread two of the jaws left hand-
                Last edited by darryl; 09-22-2009, 02:45 AM.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                Comment


                • #9
                  Quit flinching away you guys. The anticipation of learning the uses of four jaw chucks is far worse than the reality. Grow a pair.

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                  • #10
                    Originally posted by darryl
                    What I want to be able to do is quickly center a piece that may be square, may be rectangular, and will be variously sized and likely trapezoidal. It might have three sides more or less flat, then the last side rounded, or it could have one concave side and one convex side, with the remaining sides sort of flat, but not necesarily parallel. Being able to center it both ways allows me to turn it round and have it be as large a diameter as possible once all the flats are turned off. If I can't do this quickly, my next best way is to shim it in the three jaw until it's more or less centered. This doesn't hold very well, so I waste time taking light cuts until I've got all the flats removed.

                    Using the four jaw chuck would be fine if all the pieces were the same size, but that's not the case. My four jaw is a bit of a pain to adjust, and that takes up time as well, thus my desire to have this custom chuck.

                    It's a tool, and I don't mind making it. It's something that I'd like to have, not an essential. Probably a winter project.

                    I can see how to make it work using combination left and right hand threaded actuator rods, crossing at the spindle axis. This merely requires the threaded holes in the jaws to be at two different heights. It won't be hard to center these rids either, it's a matter of using some hollow setscrews around the perimeter of the chuck plate. What I will be missing is the thru-hole, but for this application I can't see needing it.

                    Now for the procedure to make these left/right threaded leadscrews- and thread two of the jaws left hand-
                    Buy two two-jaw chucks and adapt one to take the 'works' out of the other?
                    Money no object, of course

                    Edited to ask - would a 2-jaw chuck (just one!) with deep Vee jaws achieve what you're looking for?

                    Tim
                    Last edited by Timleech; 09-22-2009, 05:26 AM.

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                    • #11
                      Turning irregular shaped pieces of material. Sound like wood turning.

                      Run them between centres. Since it's plastic, you might even find the fast way to do it is with wood turning tools.

                      People seem to have forgotten that early metalworking lathes weren't even supplied with chucks!
                      Paul Compton
                      www.morini-mania.co.uk
                      http://www.youtube.com/user/EVguru

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                      • #12
                        Use a face-plate

                        This is a classic case for a fixture to be made to mount on a plate that in turn is located and bolted to the lathe face-plate.

                        It will not require a chuck and can be made from scrap. It can be mounted or demounted from the face-plate in a matter of minutes.

                        All that is required is a bit of careful job analysis and creative and lateral thinking and you are there.

                        Face-plate work is never mentioned here - but it should be.

                        It is as much an art as a craft or a science.

                        It was in common use in workshops in the not so distant past.

                        It was an essential part of every Apprentice's training.

                        Face-plates work well on rotary tables as well.

                        So if the OP has a mill and a big-enough rotary table with (or make) a face-plate - use that instead of the lathe as it will eliminate all the problems associated with unbalanced work on a face-plate on a lathe.

                        Face-plates used with a rotary table come in very handy on a shaper or slotter. Same on a boring-mill or a vertical lathe etc.

                        Comment


                        • #13
                          Originally posted by darryl
                          What I want to be able to do is quickly center a piece that may be square, may be rectangular, and will be variously sized and likely trapezoidal. It might have three sides more or less flat, then the last side rounded, or it could have one concave side and one convex side, with the remaining sides sort of flat, but not necesarily parallel. Being able to center it both ways allows me to turn it round and have it be as large a diameter as possible once all the flats are turned off. If I can't do this quickly, my next best way is to shim it in the three jaw until it's more or less centered. This doesn't hold very well, so I waste time taking light cuts until I've got all the flats removed.
                          i'm missing something. in your examples above, if three sides are square and flat, and one side is concave or convex, won't you need to adjust the jaw for that fourth side independently? it really sounds to me like a plain old four-jaw with four independent adjustments would work fine.

                          your idea for the opposed-jaw adjustable four-jaw sounds cool, but it seems like it would only be useful for square or rectangular pieces. those shapes can be set up in a four-jaw in about one minute, and i ain't no machinist.

                          andy b.
                          The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining

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                          • #14
                            Originally posted by oldtiffie
                            This is a classic case for a fixture to be made to mount on a plate that in turn is located and bolted to the lathe face-plate.

                            .
                            A Keats angle plate, as at

                            http://www.collegeengineering.co.uk/Castings/558.htm

                            when mounted on a faceplate is essentially a 2-jaw chuck, but with the advantage/disadvantage of not being self-centring.

                            Tim

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                            • #15
                              I have never found it that much a problem to center work in a four jaw regardless of the shape.

                              I have never used the four jaw with a scroll to open the jaws after centering but to me it may still need some centering after opening and closing the jaws with the scroll, especially with irregular stock.
                              It's only ink and paper

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