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Thread: 4 jaw independent independent chuck

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  1. #1
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    Default 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?

  2. #2
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    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!

  3. #3
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    Quote 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 at 10:13 PM.

  4. #4

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    Quote 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.
    .
    "Opportunity is missed by most people because it is dressed in overalls and looks like work." Thomas Edison

  5. #5
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    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

  6. #6
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    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

  7. #7
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    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...

  8. #8
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    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 at 01:45 AM.

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

  10. #10
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    Quote 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 at 04:26 AM.

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