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am i expecting too much from bison

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  • am i expecting too much from bison

    i just got my second bison 5 " 3 jaw chuck from the supplier. this is pre mounted on the mounting plate to fit my atlas / craftsman that has a 1-1/2 threaded spindle.

    anyway, i checked and rechecked the lathe, and the old chucks i had with the machine, and everything was on the mark. . .

    the last chuck i got was .007 out, so i complained to enco and they cheerfully replaced at n.c.

    the replacment is the same .007 out, but not in the same place on the spindle mount as the last. . . (i marked it on my spindle)

    i will probably answer my own question here but . . . . should i try a "set thru" i thnk theyre called or say screw it with the three jaw and just get use to using a 4 jaw ? and get a new one of those ?

    and ion a side note, i also recieved my new 6" phase 2 rotary mill vice. wow ! have it sitting on the bed of hte mill so tonite i will mount and square it up. . . and who knows, maybe try tramming the mill besides.

    i hope i have not already posted this question earlier. its the legal pharasu.. ..... DRUGS that make it hard to remember.

    thanks for whatever input i can get..

  • #2

    A few questions for you then I think i might be able to help.

    1. what model is the chuck?
    2. have you loosened the chunk from the back plate and re adjusted it to see if you can decrease the run out that way?
    -Dan S.


    • #3
      enco part number 271-4150, 5 inch

      i did not attempt to align as the backing plate or mounting plate checks out the same runout.

      the inspection tag sez 0,05 allowable i think, and the little instruction book that came with it sez, 003m .

      and now i am all ears (eyes)



      • #4
        Assuming you ahve followed some of the advice previously posted; made sure the spindle and mount are clean and true, no dings or damage, you acn make your own "adjust-tru" by removing the chuck from the back plate and taking a cut on the spigot the chuck registers on.

        Reassemble and just snug up the mounting screws and bump the chuck into line. Use a good piece of round stock in the chuck to indicate it, and be aware that the chuck might display varying amounts of runout with different diameters of stock.
        Jim H.


        • #5
          I've heard really good things about the Bison chucks, and the Bison tailstock chuck I bought is somewhere less than 3 thou runout. So nearly a ten thousandth seems a lot.

          But if you had two chucks back-to-back with the same runout, it makes me think that the error may lie elsewhere. JC posted some great things to check.
          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."


          • #6
            You can find the Bison/Toolmex work holding catalog here. (warning 20mb file)

            your bison model # is: 7-805-0552 page 68

            what you have is a type 32XX Universal scroll chuck and you can find your maximum run out listed on page 21

            Radial 0.0014"
            Axial 0.0008"

            Enco catalog confirms this.

            So either the back plate is messed up, or the plate and chuck where poorly aligned when they where bolted together. My guess is the later.
            -Dan S.


            • #7
              Buy a threaded back plate and a plain back chuck and fit the two together.Doing so will take some patience,but the runout will be within the TIR limits of the chuck which knowing Bison will be less than .0015".
              I just need one more tool,just one!


              • #8
                The problem is almost certainly with the plate......

                They are usually threaded for a universal fit, and may be stone loose on yours..... For 1.5"-8tpi, S-B is a tad small, Logan is bigger, dunno about Atlas.

                What I would do is the following, assuming the backplate is separate.....

                Check mounted chuck face and OD for true.... with an indicator. That will show you if the plate or chuck is bad.

                If chuck is "true" on OD and face, then IT is the problem. Jaws may be in wrong places, etc.

                If chuck checks "out" I would take backplate off the chuck, and see how it fits on threads. it may be loose or fairly snug. Loose generally means it won't "repeat" it's position well unless extreme care is taken. Then you may want a better backplate.

                if threads are OK, see if it has any dings where it hits the shoulder on the spindle. Stone off (or burr-file) any dings so they are flat and see if that helps.

                If fore-going is OK see if there is a "spigot" or turned protrusion that fits into the back of the chuck.
                Is that a loose fit in the chuck? if so, you can turn a better fit, usually, if the plate is thick enough. Only needs maybe 50 thou or a bit more to fit in..

                If it is OK for fit, see if the spigot indicates true..... If it seems "out", mark relative position, and take off/put on several times, checking each time....

                if the "out" is at same point every time, then you can turn a truer spigot.

                Also check for "out" on the FACE, to see if it is "camming", or wabbling. if so you can true that up. "Face" is the narrow face OUTSIDE of the spigot area. Be sure the inside area does NOT touch the chuck.

                If you turn a new spigot, etc, make it as tight a fit as possible. Then check the "out" of assembled system, on chucked part, od of chuck, and face of chuck. OD and face should be "on", not "out". If so, you have done your part, and further "outness" of part is in the chuck itself.
                Last edited by J Tiers; 10-15-2008, 11:29 PM.

                Keep eye on ball.
                Hashim Khan


                • #9
                  Check out all that Jerry discusses. Remember that registration accuracy depends on the clenliness of abutting surfaces and that no 3 jaw chuck is perfect. Event the best non-adjustible scroll chuck cannot resonably be warranted more accurate than 0.003" TIR at the jaws anywhere within the range of the chuck capacity. Those who posess thucks that are better should thank your lucky stars.

                  Yes, a three jaw chuck with an adjustable eccentric feature can be far superior in TIR than a plain vanilla one. They're worth it if you need to do a lot of three jaw work and require exceptional TIR performance. I'd have one myself if I wasn't so used to a 4 jaw after (hee hee! By cracky) 45 years as a machinist one way or another.

                  So clean up the threads, lightly stone the shoulders, chase out your source of errors and check the chuck's mounting on its backing. You may get lucky and get it close to 0.001 TIR.

                  One thing you should keep in mind is that 3 jaw chucks are delicate. Break a parting tool in the cut and you might lose a little of that hard won TIR. Rip a piece out of the jaws and you may deform the body. A small SB lathe is puny and a Bison chuck is stout but some combination of inertia and leverage may spoil your day. OTH you may evade the hazards and go on to a long career in your home shop without ever experiencing a crash in your 3 jaw chuck. You might but it's not likely. Prepare for the worst, hope for the best etc.
                  Last edited by Forrest Addy; 10-16-2008, 03:43 AM.


                  • #10
                    today i shall start the quest to find the gremlin.

                    im glad you mentioned the "crashed" cutoff tool thing. i did do that on my sheldon 13 and now that you opened my mind, i must also re-adjust that bison too. its off more than .010 after the "ouch" im sure. i gotta be more careful, or was it the boy what done it. . . . . have to check with him.

                    thanks for all the guidance.


                    • #11
                      What JTiers said about "universal fit" ....yes. The backplate has to fit every 1 1/2-8 spindle ever made, which may mean it may not fit yours very well.

                      I got a Bison chuck similar to what you have a few years ago. The fit on my lathe left something to be desired. I eventually bored the threads out of the backplate, fitted a plug, and re-threaded it. That got to be a bit of a trick, as I had to keep the threads concentric with the already-machined o.d. of the backplate. It would have been easier, I think, to start with a backplate blank so the o.d. could be turned concentric after threading, with the backplate mounted on the spindle.
                      Try to make a living, not a killing. -- Utah Phillips
                      Don't believe everything you know. -- Bumper sticker
                      Everybody is ignorant, only on different subjects. -- Will Rogers
                      There are lots of people who mistake their imagination for their memory. - Josh Billings
                      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                      Don't own anything you have to feed or paint. - Hood River Blackie


                      • #12
                        Don't go cutting yet. Check the unthreaded part of the spindle, I got two threaded back plates form Bison for a 6" Atlas, they fit sloppy as hell. Threads don't matter so much, but the stright bored portion of the plate was 1/32' over size.

                        This should be a ringing fit. I bored the back plate over size and press in a bush and bore th size plus .0005. Back plates go on tight now, after fiting the chuck, runout is now .0014 at 3' from chuck face now.



                        • #13
                          ill check that in a few minutes. thanks. i took the backing plate off the chuck. had to tap a skinny knife blade in between the two pieces to get them to come apart. got another question in a new post. .


                          • #14
                            I can fix this.


                            • #15
                              Maybe that straight part is so important, and maybe NOT.

                              I have a chuck with a loose and sloppy straight portion of the threaded spigot, and it repeats very well indeed if removed and put back.

                              That part DOES help get it lined up when starting the thread... and tend to hold it straight. It should be out of the way when the chuck is tight, or it may fight the alinement.

                              To REALLY work, that part should be split into a rear part and a front part, with threads in between. The the chuck would get started on straight and no foolin....

                              Keep eye on ball.
                              Hashim Khan