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  • #16
    So this chuck is old and worn, so how did it work long enough to get old and worn? It must of worked for someone.
    Was it wobbling before you took it apart or someone else took it apart before you? B.G.
    Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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    • #17
      I know little about it since It was in a box of parts along with the lathe. For all I know it was never used with this lathe. The faceplate and 4-jaw seem to run fine. The original owner says that his eyesite wasn't good anymore so that's why he ditched the lathe. Must have been using that chuck ;-)

      Ken

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      • #18
        Perhaps this chuck was intended for a different lathe. I wonder if the part you are calling the "back plate" is not supposed to come in contact with the spindle at all.

        The part that you describe as the main body appears to have a machined flat surface behind the threads. In my mind, this would be the best reference surfact to have in contact with the face on the spindle. Yet, if I understand correctly and if the pictures don't lie, then this surfact is not making contact. Instead, the rear surface of the part you are calling the back plate seems to be making contact with the spindle. If the main body and the back plate are not completely square then this could easily throw the overall chuck off.

        Try mounting the main body of the chuck on the spindle by itself and see if it is better that way. If it is, then it's the "back plate" that is throwing things off and that needs to be machined to clear the spindle entirely.

        Paul A.
        Paul A.
        SE Texas

        And if you look REAL close at an analog signal,
        You will find that it has discrete steps.

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        • #19
          Your chuck looks like a couple I have. But none of mine have the extra back plate you show in your third picture. My chucks are open back chucks. The extended threaded part at the back of the chuck bottoms out against the lathe spindle shoulder. This is just in front of the front bearing housing.
          Someone may have made the extra plate to cover the back of the chuck.
          BYW my lathe is a 9 inch Southbend made either late 40's or early 50's.
          Living By the Square and On the Level

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          • #20
            The chuck is assembled properly. The two major pieces constitute the body of a chuck that was an integral mount of some sort. It was not intended to be used with a backplate. A backplate is a third plate machined to adapt a chuck to a spindle.

            That chuck has been modified from some mount to what it is now. It was most likely a 1-1/2"-8 that was trashed, and someone tried to salvage by threading the body. A likely scenario is, not finding a good surface to indicate, or having difficulty holding it to thread, a piece of stock was chucked in another chuck, this chuck was reversed and clamped to the stock by it's jaws and machined. This resulted in three sources of runout and induced the wobblies.It probably spent the rest of it's life in a drawer or box of other experiments somewhere.

            A good use for a chuck like this is to attach it to a suitable piece of flat stock and use for as a vise for holding round stock on the rotary table, milling machine etc.
            Jim H.

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            • #21
              The chuck will bottom out on the threads before it gets to the spindle nose so there is no way to get it to seat against the nose, the backplate must be on. Just spinning it on until it stops the thing still looks like an unbalanced top.

              I got the new Bison chuck today, spun it on and it is noticably better. But.... it is .005" at it's worst. I went a little deeper and found that the chuck seats against the spindle bearing shield which has a .005" dip at that point. Actually it's pot marked! Seen better days but I guess that one area is worse than the others. The spindle nose (or shoulder) itself is dead nuts (barely .0005") But it looks as if the bearing shield is actually what the chuck seats against. Logan doesn't carry the shield any longer and I haven't seen anything on Ebay in awhile so I guess I'll just keep my eyes peeled.

              http://www.kenrinehart.org/spindle.jpg

              Funny thing is, even though the chuck is out .005" I've finally been able to use the lathe and have been making stuff all day !!

              Ken-

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              • #22
                So make a spacer ring that goes against the end of the lathe spindle where the threads are stopping the chuck.

                That way it seems it would stop against your spacer, not on the threads or the bearing shield.

                Is the bearing shield part of the bearing? Could the bearings NOT be seated correctly or perhaps the wrong part number???
                Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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                • #23
                  The shield is up too far.....that's all. You should be able to tap it back.

                  Adding a spacer works, but adds another interface and dimension with accompanying errors.

                  If the chuck didn't seat, its no wonder it was out 0.017.....it might be OK after all.
                  CNC machines only go through the motions.

                  Ideas expressed may be mine, or from anyone else in the universe.
                  Not responsible for clerical errors. Or those made by lay people either.
                  Number formats and units may be chosen at random depending on what day it is.
                  I reserve the right to use a number system with any integer base without prior notice.
                  Generalizations are understood to be "often" true, but not true in every case.

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                  • #24
                    On the new chuck the threads are further back inside the backplate so the chuck doesn't engage "as many" threads as the other units I have so no there is no way to "bottom out" or run out of thread. Maybe a 1 set of thread difference. When I look at the bearing shield closely with a scope it tells a story It's pretty riddled and is easy to see that it isn't true. There are waves and dents in it. I believe that the bearing shield is screwed onto the end of the spindle, at least that's what I see in the part's diagram.
                    Don't quote me on that. If so this would limit any movement up or down since I have no idea how they would have installed it. I'll take a look further tonight. I don't feel any play in the spindle itself.

                    The spacer may be a nice temporary fix to check. Going to need some steel for that. Only been using T6 up to this point ;-)

                    Ken-

                    [This message has been edited by kenrinc (edited 12-30-2004).]

                    [This message has been edited by kenrinc (edited 12-30-2004).]

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                    • #25
                      The chucks, both old and new need to "seat" against the lathe spindle face, not the thread or bearing shield or anything else, that is the problem. My guess you could take a class 8 SAE 1 1/2 inch flat washer and use it to make a temporary spacer. I would be nice to have a surface grinder to make the spacer as true as you could. B.G.
                      Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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                      • #26
                        The chuck must fit directly against the shoulder of the spindle for the best accuracy. If the bearing shield is interfering with that fit, correct the situation. J Tiers has spent a lot of time with a Logan spindle, and knows what is involved. Listen to him and tap it into place. Spacers will only add problems.
                        Jim H.

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                        • #27
                          Here is a pic of the spindle and shield outside teh unit.

                          You can see the shield is a stamping which is just pressed on. You should be able to tap it down. Mine is about 0.015 or so lower than the "shoulder". I don't know how far down it can be before it rubs. I suspect from looking at mine that you have a "window" of at least 0.040 or so.

                          BTW, you should have the bearing writeup in your inbox. I sent you a "warning" message first so you would know you are getting attachments.


                          [This message has been edited by J Tiers (edited 12-31-2004).]
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment


                          • #28
                            Thanks bud! Anyway, tapped down the outer cover tonight, it was high in places but now it's noticably lower and when I thread a chuck on I'm pretty sure it's seating against the spindle shoulder and not the bearing cover. Even so it didn't change anything. The chuck itself has quite a bit of leeway, in other words it's loose as I thread it on and doesn't become tight until it snugs up to the spindle shoulder. Still looks like it's spinning slightly eccentric. I can't feel any play in the bearings other than rotational play, no back to back or side play at all.

                            Ken-

                            [This message has been edited by kenrinc (edited 12-31-2004).]

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