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  • Help with pin chuck design

    Can anyone explain pin chucks to me? Is there a relationship between the diameter of the mandrel and the diameter of the pin? Or is it not that important. We are wanting to use one for turning the O.D. profile of a nylon bushing.

  • #2
    I have what was called a pin chuck, and it's basically just a tubular handle with a sort of collet closer on the working end. It will close onto any drill bit up to about 1/16 inch or so. It's pushing it to open it that wide. It has a spinner on one end so you can put finger pressure there, then rotate it with the other hand to drill the hole.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #3
      The type I need info on looks like a mandrel with a flat on it and a pin fits in the flat. The part locks on when rotated. It looks something like this.
      http://www.fholder.com/Woodturning/pinchuk.gif

      [This message has been edited by slink74659 (edited 03-17-2006).]

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      • #4
        I posted this a while back, http://bbs.homeshopmachinist.net//Fo...ML/015445.html

        I called it a stub arbor. It kind of depends on the material at hand as much as anything. If you are turning nylon, which requires little force, a small pin will work. Depending on the thickness of the wall, there will be some deformation, and the smaller the pin, the less it will effect it.

        [This message has been edited by JCHannum (edited 03-17-2006).]
        Jim H.

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        • #5
          In the book the Shop Wisdom of Philip Duclos he wrote a short article on how to make one. He calls it a temporary self locking stub mandrel. He says that the depth of the flat is controlled by the diameter of the locking pin you are going to use and that roughly a ratio of about 12 to 1 between the diameter of the stub and the diameter of the pin works well. I usually use what ever pin material I have that is close that will do the job. He says to measure over the pin when cutting the flat and it is deep enough when the reading is about .002 smaller than the diameter of the bore the mandrel is being made for. This method works real well but you must take light cuts or you can spin the part on the madrel. I turned a flywheel for a model ic engine and I can't detect any runout at all. Get the best fit you can when turning the mandrel to fit the bore of the part and you should get good results also. I highly recommend the book by Philip Duclos by the way, it is filled with other neat tricks too.
          Jonathan P.

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          • #6
            I would reccomend a regular expanding mandrel. the type with a tapered screw in the end.

            that pin thing looks like monkey business handy for turning something in a blind hole but unsuitable for a lathe work. it would require serious good fits to work worth a darn.

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            • #7
              <font face="Verdana, Arial" size="2">Originally posted by dsergison:
              I would reccomend a regular expanding mandrel. the type with a tapered screw in the end.

              that pin thing looks like monkey business handy for turning something in a blind hole but unsuitable for a lathe work. it would require serious good fits to work worth a darn.
              </font>
              As the old saying goes, "Don't knock it until you have tried it." It is a proven method that has been around for quite a while. I have the expanding mandrels, and make them as needed when the occasion arises, but the stub arbor as described works very well, and is much easier and faster than the expanding mandrel.

              As with any work holding device, it has advantages as well as disadvantages.
              Jim H.

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              • #8
                <font face="Verdana, Arial" size="2">Originally posted by JCHannum:
                As the old saying goes, "Don't knock it until you have tried it." It is a proven method that has been around for quite a while. I have the expanding mandrels, and make them as needed when the occasion arises, but the stub arbor as described works very well, and is much easier and faster than the expanding mandrel.

                As with any work holding device, it has advantages as well as disadvantages.
                </font>
                I totally agree with JC. With a little experience it isn't that hard to achieve a very good fit between the mandrel and the part which in turn gives great repeatability when taking the part off and on if needed. Another great thing about this method is that you can use just about anything you have laying around to make one. Those expanding mandrels are nice but you have to have one on hand before using it. The beauty of this trick is you just go to the scrap box for material. If you have multiple parts it can be a real time saver also.

                Jonathan P.

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                • #9
                  Thanks for the info JCHannum and japcas. That is what I need to start. Easy and fast is what we need for the short run production.

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