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Poor surface fiish.

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  • Poor surface fiish.

    Last night I was turning the rusty layer off some 1” 4140, that produced a mirror finish in the past. Now I was looking at a shiny part with a spiraling rope like texture. The extension out of the six-jaw chuck was about 3”. Next pass I set the live center in the end of the work and things got better but there was a little of the same kind of visible pattern. The work piece was a little longer than the headstock. Normally I run a four-jaw type fixture in the outboard end to help support the work.

    Did the finish pattern result from vibrations related to the unsupported end?
    Byron Boucher
    Burnet, TX

  • #2
    It's either what you said or something not 100% kosher with your tool... or something else is loose somewhere allowing a vibration.
    This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
    Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
    Plastic Operators Dot Com


    • #3
      Last time that happened to me I sharpened the cutter and got back to normal.

      Not 4140 though.

      My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."


      • #4
        Indexable tool? check insert for very slight looseness or a very slight chip on the tip.
        CCBW, MAH


        • #5
          Rust can dull a cutter very quickly, particularly if you don't cut it aggressively. The dull tool can then chatter. Remove the tool and examine it under magnification. You may find a sharp, freshly ground cutting edge but on the back side a small curved "flat" which provides absolutely zero clearance which can cause lots of chatter.


          • #6
            Both - tool dulled by rust caused enough vibration to loosen the gibs on the compound slide or tool post


            • #7
              Quote: "Now I was looking at a shiny part with a spiraling rope like texture" Curious, I have the same problem, only when I use my TOS 6 jaws chuck...


              • #8
                ..."I have the same problem, only when I use my TOS 6 jaws chuck"...

                The pattern you describe says the chuck is grabbing the work piece at the rear ONLY
                In other words, the jaws are sprung and need grinding.
                You can confirm this by taking a cut, then remove the workpiece and wrap a ring of paper about 1/2 inch wide so the tips of the jaw grip the stock where the paper is. ( Masking tape works, but not plastic/rubber) and recut the workpiece
                Grabbing the piece both at the base ( near the scroll) and at the paper is like placing a shim at the jaw tips
                On some old lathes and worn chucks, it was common years ago to use brass shim stock to solve the problem

                If the trouble persists, its the tool bit ( or in remote situations-bearings)
                If the trouble clears, its the chuck.
                This is a commonly problem seen after a big crash

                Green Bay, WI