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Accuracy of Jet 18 PF

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  • Accuracy of Jet 18 PF

    I noticed that a small drill bit in my mill/drill was wobbling a bit so I put an indicator on the outside of the chuck and found it was a couple of thou out of line. I took the chuck off the arbor and found the arbor was running about a half thou out.
    Is this normal and if not, what can I do about it.
    Any help would be appreciated.

  • #2
    I don't think you're going to get a mill/drill any better than that--they're just a glorified drill press...
    Just one project too many--that's what finally got him...


    • #3
      You have to indicate every posibillity, anytime you want to minimize run-out.
      Go either way drill to the receiver or visa versa.

      I'd validate my spindle first, not just in one place.
      R8? at the rim and again just before the taper meets the bore.

      Spindle receiver good.
      Then the chuck-shank at the Jarno or what ever it's pressed on to.

      Chuck good.
      Turn the drill a bit, third or quarter turns.
      Try another bit....

      Getting the picture here?
      Last edited by Old Hat; 08-27-2014, 02:05 PM.


      • #4
        The potential for run out can be caused by many things. Dirt on the jaws is a favorite, bent spindle, bad bearing etc but look at the simplest things first. Drill chucks are not really precision devises, at least most aren't. Half a thou on the spindle of a mill/drill isn't bad.
        The shortest distance between two points is a circle of infinite diameter.

        Bluewater Model Engineering Society at

        Southwestern Ontario. Canada


        • #5
          The good thing is that milling and drilling accuracy won't be too dependent on the spindle runout if done properly.


          • #6
            so what is the runout of a ground pin in the chuck measured at 10x diameter from the chuck? if that is anything close to 0.002" your a lucky guy.


            • #7
              Put the ground pin in a collet and measure, it will probably tell you the runout is in the chuck, arbor, or both.