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  • Acceptable runout?

    Trying to get my Indian three jaw chuck on my WWII Sheldon lathe concentric.....if that's the right word. Close as I can come so far is +-.002. Is that good enough for hobby use? I'm trying to make ferrules for a ramrod for my English muzzleloading shotgun right now, can see a difference in the parts when they screw together, nothing major, but not up to English best quality....Pete

  • #2
    Pete, That would not be acceptable to me, but it depends on the work you do and the required accuacy you desire.
    But first, without doing any modifications you will be advised to do, you need to do this on your 3 jaw.
    Mark each of the 3 socket holes with a magic marker and then only using one of those holes, tighten on a known round pin and indicate your runout. Then loosen entirely and re-tighten with the second hole and recheck, then repeat for the third hole. Every chuck is different, and one socket is always supreme in accuracy Paint that socket White with nail polish, or paint the other two red so you do not use them for "tightening but loosening can be done with any.

    The reason for the above is the scroll plate can move a little bit you need to mark the best location.
    If you ever grind the jaws, it is critical to know which socket was used for the grind setup and to use that at all times.
    Rich
    Green Bay, WI

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    • #3
      Originally posted by wygant View Post
      . Close as I can come so far is +-.002. Is that good enough for hobby use?
      I push back on "good enough for hobby use" thing in that the runout needs to be good enough for task/function at hand, whether its hobby or commercial shouldn't matter. That aside, .002" from a three jaw is excellent. Most would have more runout than that....and if you need it better you use a collet or the 4 jaw (or make a bored sleeve). Keep in mind all ops you do without disturbing the work will be as concentric to each other as the spindle and its bearings....which is why very often with the proper planning of the work the amount of 3 jaw runout doesn't matter.
      .

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      • #4
        The run out amount acceptable is entirely up to you as they are your parts.
        If however you have a concentrcity call out on a Customer Drawing and the customer can measure it a different approach may be required.

        I recently drilled centers in each end of a bunch of shafts, the Customer required .0002" deviation between the center and the OD as they would be measured in a test center with a CMM.
        One guy here made 10 by drilling from the tail stock, all were rejected.

        I made 10 new ones using an adjustable 3 jaw chuck, then drilled and reamed a block of steel held in a QCTP holder with tools held in the chuck then did not move anything, placed the center drill in the reamed hole in the holder held by set screws. Drilled 20 ends after adjusting the chuck for each end and they passed inspection.
        This was all very very time consuming as in 6 hours to drill centers in the ends of ten 14MM X 350MM long shafts.

        If making parts for yourself YOU decide what the accuracy should be rather then someone else telling you what THEY want.

        By the way .002" is excellent for a scroll chuck that is not adjustable and you are unlikely to do better so have at it.

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        • #5
          His runout is .004"
          He said + and - .002

          Rich
          Green Bay, WI

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          • #6
            Gawd! Does no one keep a bumping hammer and cig rolling paper at hand!???

            Any level of precise can come from those two adjuncts. Starting at .002" would be a boon.

            Yes, You are doing fine, get on with it. Hell, I can't even see two thousandths when they are laid side by each.

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            • #7
              .002 out of a three-jaw is not bad -- most are far worse. You'll have to try something else to get the runout lower. Maybe bumping it a bit, or cig paper like Cal said. FWIW, most ordinary notebook paper is around .002 or .003 in my experience. Is there any way to do the job between centers? That is the most accurate of all.

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              • #8
                Originally posted by CalM View Post
                Gawd! Does no one keep a bumping hammer and cig rolling paper at hand!???

                Any level of precise can come from those two adjuncts. Starting at .002" would be a boon.

                Yes, You are doing fine, get on with it. Hell, I can't even see two thousandths when they are laid side by each.
                Don't need it in the year 2019 when adjustable 3 jaw scroll chucks are widely available.

                Comment


                • #9
                  It wouldn't be acceptable for me, but I'm fussy. It all depends what you looking for as far as accuracy.
                  My Clausing 5900 came with the original Buck 3 jaw. The run out was about .005. The first thing I did when I got the lathe was replace it with a Bison 6 jaw set tru.
                  I have no regrets about buying the Bison chuck.

                  JL....................

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                  • #10
                    Wygant, is the part machined in one clamping, or is work turned around and re chucked.
                    If it's re chucked, you will find most chucks not up to task.

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                    • #11
                      0.002" runout on a foreign 3-jaw is actually pretty good - for what it is.

                      If you want to get a three-jaw chuck dialed in to dead-nuts-on, then you need something like an "Adjust-Tru" chuck. If you want to get your chuck to be dead-nuts-on, then you might need to grind your jaws when you have them clamped down on a precision-ground ring.

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                      • #12
                        DO NOT BOTHER to grind jaws if you are trying to improve accuracy.

                        The only reason to grind the jaws would be that the jaws are bell-mouthed, or otherwise damaged.

                        Grinding is of no particular use for accuracy, unless you are working with a 2 part soft jaw, and are doing a setup for a particular part. Then you will be always working at the same point on the scroll.

                        A 3 jaw scroll chuck is a compromise, and is never going to be especially accurate. Maybe there is a difference between 0.002" and 0.004" as an error, but all I see is "an error", the argument is just about how huge it is. Just never expect a scroll chuck to be accurate, and you will be OK.
                        1601

                        Keep eye on ball.
                        Hashim Khan

                        Comment


                        • #13
                          I think you got a german made chuck that is rebranded by the Indian reseller. The comments of "not good enough for me "I think refer to the end product,not the performance of the chuck run out.

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                          • #14
                            There are various work-arounds for your problem. Below is a quick and dirty one but it will work.

                            Take a piece of expendable round stock larger in diameter than your workpiece and drill and tap a couple of holes at 90 degrees to each other and 90 degrees to the centerline of the stock. Put it in the 3 jaw and do not remove it for any reason till the job is done. Next drill and precision bore the round stock to the exact diameter of the O.D. of the part you need to work on. Your part should be a very close slip fit into the bored hole. Tighten the screws and you should be running dead true to the bearings of the lathe which is as accurate as you are going to get on that particular machine. For screws use No-mar set screws (plastic tipped) or brass to protect the surface of your workpiece.

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                            • #15
                              I agree that .002" runout is very good, as is .004" runout on a three jaw, I have like .010" runout a lot of the time on my worn out chuck. Have got to work around it. I am planning to buy an adjustable 3-jaw chuck so I can dial in the last thousandths. I've also shimmed the 3-jaw from time to time.

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