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lathe chuck with four jaws that has a scroll and individual jaw adjustment?

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  • #31
    The back of this chuck doesn't seem to have a tapered register for the backplate. (snuck in a little Germanthere.) Is that normal? I can't believe only the mounting bolts are used to register the chuck to the back plate.
    Location: The Black Forest in Germany

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

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    • #32
      Just for the record, not all combination chucks are scroll chucks.

      I have an old Skinner four jaw, about a ten inch. The jaws are all operated by full length screws, which cannot be disengaged from the body of the chuck. Just like a standard independent four jaw. Each of the screws has a spur gear near its outer end, which engages with a large ring gear out near the circumference of the chuck. Turn any one screw, and they all turn.

      So, how can it function as an independent chuck? Simple. Underneath the ring gear is a separate ring with ramps that mate with ramps built into the chuck body. A screw knob on the back of the chuck allows you to rotate that ring a few degrees, which will raise or lower it on the ramps - thus engaging or disengaging the ring gear from the jaw screws.

      I think that it’s actually a stronger design than a scroll chuck, but there is a compromise. Each of the spur gears has maybe 24 teeth - I haven’t counted - so if you need to do any really fine tweaking in the independent mode you will likely have to tweak a jaw or two back again to get the ring gear to mesh. But then, if the top jaws have been ground accurately at any one setting, they should be accurate at all settings. The ring gear won’t wear or shift as a scroll does, and should be more accurate.

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      • #33
        Originally posted by Black Forest View Post
        The back of this chuck doesn't seem to have a tapered register for the backplate. (snuck in a little Germanthere.) Is that normal? I can't believe only the mounting bolts are used to register the chuck to the back plate.
        Please post a picture/s.

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        • #34
          Here is a picture of the back of the chuck. Click image for larger version

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          Location: The Black Forest in Germany

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

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          • #35
            This chuck is definitely a scroll and independent. No gears except to turn the scroll
            Location: The Black Forest in Germany

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

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            • #36
              the backplate registers will be a) the flat part the chuck bolts too and b) and a small lip that interfaces with the inside diameter of the bit of the chuck that the bolts go through.

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              • #37
                The matching step on the front of the backplate should not reach the inner part of the chuck. It should be square, not tapered.

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                • #38
                  Originally posted by Black Forest View Post

                  Plain as day. Floorsandingmachinerental...........what is the problem?
                  Yeah , I saw that too..easy to read and saves spaces..

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                  • #39
                    I dont think a register needs to be tapered, it just has to fit.
                    I made a drill extender for a corded drill . 1/2 cold roll about 6 inches long , goes on threaded spindle.. register lips.. it works great ...runs straight, leave it on all the time.,

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                    • #40
                      Apologies for a slight digression, but I have just seen this vise on ebay which also has individually adjustable jaws. Ebay UK 333857595248.

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                      • #41
                        Black Forest,
                        German language- difficult language.
                        I as a native speaker -German- have the complete correct grammar also not in use. Is it now "(der)The brook" or "(die)The brook" A brook is a very small river.
                        The much bigger problem are, the many Anglizissmen in the German language.
                        Here in the southwest, the French language has also left its mark.
                        With you in the Black Forest, the Alemannic dialect also plays a very large role.
                        Many greetings from the southwest of Germany.
                        Bruno
                        http://www.mueller-bruno.de

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                        • #42
                          Originally posted by Bruno Mueller View Post
                          Black Forest,
                          German language- difficult language.
                          I as a native speaker -German- have the complete correct grammar also not in use. Is it now "(der)The brook" or "(die)The brook" A brook is a very small river.
                          The much bigger problem are, the many Anglizissmen in the German language.
                          Here in the southwest, the French language has also left its mark.
                          With you in the Black Forest, the Alemannic dialect also plays a very large role.
                          Alemnnic is the worst. We have neighbors that I don't understand anything when they speak. My wife a native German speaking person says she doesn't understand a lot of them either. What town do you live in Bruno?
                          Location: The Black Forest in Germany

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

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                          • #43
                            In the UK, we have loads of dialects, some of which are difficult to understand. There was an electrician from Wolverhampton installing something at work, and I thought he was speaking a foreign language. I even had difficulty understanding what somebody from Southampton was saying. The funny thing is that everybody in the country can understand the standard English spoken by a newscaster on a national channel.

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                            • #44
                              I was told that the chucks were known as 4 jaw universal chucks. That is how they were described in my apprenticeship books. As opposed to 3 jaw universal chucks that we know as 3 jaw chucks.
                              Sarge41

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                              • #45
                                Whether they are called combi or universal probably depends on your particular part of the world. Bison make this style in 3 and 4 jaw variations, they call them combi, which is where I got that name from.

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