Announcement

Collapse
No announcement yet.

3 jaw scroll chuck with individually adjustable jaws

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 3 jaw scroll chuck with individually adjustable jaws

    As the title says I found a 3 jaw scroll chuck that you can adjust the individual jaws also. Is this a common chuck? Does it have a name it would be called?
    Location: The Black Forest in Germany

    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    Set Tru or Set True...
    Driebackfutter..

    Comment


    • #3
      Thank you. I was under the impression that a Set Tru chuck was centered on the back plate with adjusting screws not that the individual jaws were adjusted to center the workpiece.
      Location: The Black Forest in Germany

      How to become a millionaire: Start out with 10 million and take up machining as a hobby!

      Comment


      • #4
        A picture of the offending chuck.
        Location: The Black Forest in Germany

        How to become a millionaire: Start out with 10 million and take up machining as a hobby!

        Comment


        • #5
          Originally posted by Black Forest View Post
          Thank you. I was under the impression that a Set Tru chuck was centered on the back plate with adjusting screws not that the individual jaws were adjusted to center the workpiece.
          Thats my understanding also about "Set True" variety. BUT there is also exactly the version you are looking for e.g. http://www.practicalmachinist.com/vb...d-help-149585/

          "Combination chuck" seem to be closest to correct name:
          http://www.lathe-chucks.com/BISON/BI...ION-CHUCKS.htm

          or not:
          http://www.bison-bial.com/lathe-chucks/4505-200

          And I would say that its pretty rare beast.
          Location: Helsinki, Finland, Europe

          Comment


          • #6
            Because they are a 'good' idea that doesn't work.

            Stick your bar and tighten it up then clock it true using the separate jaws
            Now remove the bar, refit to the chuck and tighten up and then clock it again and it will be out as one of the separate jaws will have lost it's 'tweaking' pressure.
            Same things happens with a 4 jaw if you remove a bar and replace it with a new one time after time, even if you use the same two jaws.

            Where they could be useful is turning eccentrics on a production basis as long as the tolerance was within limits.
            .

            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



            Comment


            • #7
              Both Rِhm and Bison call them "Combination Chucks", either 3-jaw or 4-jaw.

              Whether they are a good idea is another question. I have a Rِhm 4-jaw, and the repeatability when using the scroll is so-so...

              Comment


              • #8
                Great Idea if they do work!

                Comment


                • #9
                  Adjusting 3 jaws to center something is a non-linear relationship.
                  If I had one like that, it would become a Christmas tree stand
                  or a door stop.

                  -Doozer
                  DZER

                  Comment


                  • #10
                    I have the Rolm 4 jaw combination chuck. I love it... way more than my set-tru chucks, and for "not round" parts, it excels. Does it repeat to 10ths? no... certainly not, but it get you very close (repeat close) with the scroll and is easy to tweak the individual jaws.
                    Last edited by lakeside53; 06-08-2017, 11:27 AM.

                    Comment


                    • #11
                      The Burnerd Griptru three jaw is a very different type and quite common on British machines anyway. Often found on cylindrical grinders, you use an allen key and black magic to adjust them...can get your work piece running spot on. The adjusting screws are roughly at 90 degrees to the jaws and work via a mysterious system that no one has ever figured out...

                      Comment


                      • #12
                        Originally posted by Doozer View Post
                        Adjusting 3 jaws to center something is a non-linear relationship.
                        If I had one like that, it would become a Christmas tree stand
                        or a door stop.

                        -Doozer
                        That's funny! I bought NOS 4 jaw 24" chuck, back plate & wrench for the opening bid of $5. It was the lot after the lathe it went on so I wondered what to do with it & thought of Christmas tree stand.

                        Comment


                        • #13
                          Originally posted by Peter S View Post
                          The Burnerd Griptru three jaw is a very different type and quite common on British machines anyway. Often found on cylindrical grinders, you use an allen key and black magic to adjust them...can get your work piece running spot on. The adjusting screws are roughly at 90 degrees to the jaws and work via a mysterious system that no one has ever figured out...
                          You mean like this: http://web.onetel.com/~duttondock/Pi.../griptru-1.gif
                          Amount of experience is in direct proportion to the value of broken equipment.

                          Comment

                          Working...
                          X