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Spindle runout ?

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  • Spindle runout ?

    Just say you have .0004TIR and no play in the bearings. Will a Adj. True type chuck dial in any closer. Thanks Glenn

  • #2
    If the bearings are lubed, it's been run for a little while and the 0.0004" is in the same spot every rotation, then the 0.0004" is probably in the spindle nose and the adjust true should remove it.

    They can be adjusted pretty close to zero but that zero point may only be at one spot, close to where your test bar exits the chuck. Move further out and things can change, especially when you're indicating low tenths.

    When adjusting for real low numbers, be sure that the chuck's face bolts are just gently snugged during adjustment. On the adjustment bolts, I use two wrenches, one above the chuck and one below. This gives better control. Once you've got it where you want it, carefully tighten the face bolts in several passes around the chuck, sort of like head bolts on an engine, alternating them. Sounds anal but I can get down around 0.0001" when I need to.



    • #3
      Is there any reason not to use a 4 jaw chuck when going for tight tolerances like this?


      • #4
        I prefer the 3 jaw set-tru over a 4 jaw because you only chuck it once and then center the chuck instead of chewing up your part. It seems to make more sense and the other thing I've noticed is that most 4 jaw chucks have big, gnarly jaws (and rightly so) so that they can exert maximum clamping force.

        Most of the stuff I do is smaller, precision parts. If I were trying to keep large, heavy work in the chuck, I'd probably reach for the 4 jaw. Likewise for eccentric or odd shaped parts ... 4 jaw is the way to go.

        Added - the set-tru was last adjusted a few months ago and anything round that I throw at it is centered within about 0.0004" ... on a par with 5C collets but lacking the "rigidity" of the collets on small rod diameters.

        [This message has been edited by nheng (edited 04-18-2005).]


        • #5
          4-jaws vary....the one that came with my Logan 10 wouldn't hold anything under about 5/8 inch diameter. Probably it had been ground a few times.

          The Bison replacement I got will probably hold a 1/8 or 3/16 piece. In any case I have not had any problem with it holding small stuff.

          Keep eye on ball.
          Hashim Khan