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  • atlas/craftsman 618 accuracy

    Hello everyone,
    I hope I can make use of your expertise to answer some curiosity on my part. I've had an Atlas 618 for a good long time; I am, however, a rank beginner when it comes to machining. About the only things I've ever made are a few firing pins and the milling on a couple of double gun bolts.

    Recently I bought one of the Headstock Jacobs Chucks for the little machine because the Atlas Lathe manual talks about how accurate they are. So, when I got the Jacobs Chuck I was disappointed to find that I got a runout of .003".
    The fellow from whom I'd bought the chuck suggested that I check the runout on the headstock spindle. Measuring on the headstock dead center, I got a runout of .0005", that is, half a thousandth. Then I sharpened a bit and carefully cut a piece of steel using both my "new" Jacobs chuck and my three jaw chuck. I got .00025" (a quarter of a thousandth) runout using the Jacobs chuck (I wonder what I'd done to get .003" the day before...something stupid apparently) and .002" using the three jaw chuck. Those figures look good to me, but, since I'm self taught from books I really have no idea if that is good for a little Atlas or for that matter any lathe.

    So, if any of you have actually measured your spindle runout and your chuck runouts, I'd be pleased to hear what figures you got. And anyone who'd care to comment on my Atlas is welcome to do so. I'll be pleased by positive comments and my feeling won't be hurt by negative judgements. Like my trap shooting scores, my ego is not dependent on the accuracy of my lathe!

    Thanks all,
    John P

  • #2
    Once you take a cut, you are measuring the run-out of your spindle bearings.

    To measure the run-out of a 3 jaw chuck, you must chuck a known round and straight bar of the size of interest. Run-out will vary depending on size of material in the chuck and what key hole you use to tighten the chuck.
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    • #3
      The Jacobs headstock chuck is relatively accurate when new. However with use, runout can build up for a number of reasons. 0.003" is not great, but probably about the best that can be expected from a chuck with some miles on it.

      They do share the jaws of standard Jacobs chucks, and jaw replacement might improve it somewhat, but I would not expect a great improvement. The main advantage of the headstock chuck is in handling small workpieces.
      Jim H.

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      • #4
        IMHO the new Jacobs chucks are not close as good as the older ones.
        "Let me recommend the best medicine in the
        world: a long journey, at a mild season, through a pleasant
        country, in easy stages."
        ~ James Madison

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        • #5
          Compared to the Jacobs headstock chuck I bought (1 1/2" - 8 thread mount), you did pretty well. Mine new out of the box has 0.007" TIR. The lathe spindle is fine; I can't detect any runout, all, on a pin held in one of my Hardinge collets.

          I keep thinking I should grind the jaws sometime.
          ----------
          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.
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          • #6
            Atlas 12" lathes were only guaranteed to .001" accuracy 1" from the chuck!! My first metal lathe was a Craftsman/Atlas 12".

            Back in the 70's,IIRC,.003" runout from a NEW Union 3 jaw chuck(which I still have 2 of) was considered good.

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            • #7
              As J mentioned , the hole you use to tighten your chuck will change the runout. This applies to your Jacobs Chuck as well.
              Any scroll operated jaws is affected by scroll eccentricity or run out.
              Get some nail polish from your wife and mark the holes with different colors ( nail polish dries super fast and will not wear off like felt markers)
              Try checking one at a time and see which is best.
              Also when using a dead center in the headstock taper , mark the spindle and the center with paint and then turn the center and redo the indicator bit again to find the best place for least runout.

              All my centers, even the ones for the tailstock are marked.
              It may only be a few tenths on some, but at least i know its close or right on.

              Rich

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              • #8
                Thanks and a qeuestion

                Back in the 70's,IIRC,.003" runout from a NEW Union 3 jaw chuck(which I still have 2 of) was considered good.[/QUOTE]

                First of all, a hearty thank you to you who took the time to respond to my question. If I'm reading things correctly, I can feel quite good about the little Atlas.

                Another ignorant question: What does "IIRC" stand for?

                Thanks again,
                John P

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                • #9
                  (If I recall correctly.) So many abbreviations I still don't know.

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                  • #10
                    Sheldon lathe runout specs were to be within 0.003" 3" from the chuck jaw with a test bar of the hole diameter. Subject to chuck inaccuracy. Sheldon lathes are no slouches when it comes to accuracy, and this number compares to the Atlas specs, so Atlas is within what would be considered industry standards.

                    The more important specifications relate to how the machine performs. Sheldon's standards for roundness are within 0.0003" with work mounted in the chuck and cylindrical within 0.0003" for a distance of 3" with work mounted in the chuck.

                    Sheldon specs for collet chuck runout are 0 to 0.001" 1" from the spindle.

                    Atlas lathes are lightweight, but are not inaccurate if in reasonable condition. They were used by the thousands during WWII for production work producing precision instrument and other parts. The 618 is a very good lathe for its size.
                    Jim H.

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                    • #11
                      The 618 is a very good teacher!!

                      Al

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                      • #12
                        Hello Jim H,

                        Thank you for the Sheldon information. Even I know that Sheldons are considered excellent lathes. And thank you for the comment about all the Atlases used during WW II. I had known about that, but it was nice getting the idea reinforced. And that used within their limits, they are fine machines. I'd also noticed that in the few professional machine shops I've had occasion to visit, there is almost always an Atlas/Craftsman or two sitting around...perhaps not the main machine, but definitely used.


                        I suppose the main reason I began to wonder about the accuracy
                        of my 618 was that on other machine tool web sites it appears to be fashionable to bash Atlases. I'd rather hoped that was the machinery workers' equivalent to the old martial arts movie, "My Kung Fu is better than your Fung Fu!" And your comments, along with the others who have so kindly taken the time to respond, suggest that I was correct in my hope.

                        Cheers,
                        John P

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